Of course you need something to bring to table in modern times, to be a productive member of society. However, that doesn't mean to specialize to the extent that you lose all context. Dig deep, sure, but come up for air sometime and take a look around. You'll be surprised at what you may discover.
I think the reason every reasonable person doesn't just do this without needing to read an article to remind him of the value of doing so is that it's really hard to do in these modern times.
Before I graduated from high school and started working in tandem with college (which rapidly escalated into a full-time career development path and compelled me to drop out, eventually), I used to hold a lot of people in deep contempt for being so ignorant and narrowminded at a time of historically unprecedented access to a never before seen breadth of information; between the Internet, book sellers, public libraries, universities, etc. there's just nothing you can't learn about if you want to these days.
What I had no concept of is that after you come home from a 10-hour day at an intense job, even a technical white-collar job that seems physically undemanding from a superficial perspective, all you want to do is just veg out; even then, there are too many other bullshit errands to do. It's not just strictly a matter of time being available logically; it takes energy, mental and spiritual, to come home at 7 PM and then compose symphonies until bed time.
Some people are more insistent than others at doing what they want to in spite of what they have to, but it's not reasonable to expect most people to do that even if the availability is technically there. We may have it easy compared to our ancestors from many economic and physical points of view, but that doesn't mean we aren't plagued with some of the problems existentially perennial to the economic man.
EDIT: Also, I am not sure that the "echo chamber" that characterises Valley web startup culture is any more sealed or myopic than the echo chambers of other comparably specialised combinations of professional endeavour. Ever seen what financial instruments traders breathe, eat, snort, etc. 24/7? People who participate in insurance industry MLM schemes? People "tracked" for "blue-collar" skilled trades? People who love and excel at working on cars or motorcycles? Realtors, mortgage brokers? I'm talking about the folks that are on top of their game in those respective sectors - the "hackers" - not the most bromidically average, uninspired 9-to-5ers. It's very similar.
Certainly can't argue with that. I'm just trying to provide a useful account of why people who play the game play it with the total commitment that they do.
It's getting more and more that doing something in particular passably - let alone well - requires thousands if not tens of thousands of hours of practice, and complete immersion and thirst for information within that knowledge domain.
Healthy or not, it's how the world works. If you spend that much time learning to be a good hacker and developing both the passion and understanding to create interesting software products, just about anything else you do "once in a while" is something in which you're going to be no more than a mere dabbler. Of course, there are exceptions; I know several Renaissance Men that seem to be impeccably good at numerous things that constitute universes of very non-trivial complexity in themselves, and have always been omni-curious, well-read, and just generally knowledgeable about, well, just about anything. But they are the exception, and even in their case, areas of sweeping general knowledge don't have the same economic or practical utility as narrow corridors of highly specific knowledge.
It's just a trade-off of the epoch in which we live. There are only so many hours in the day, and that's just how it goes.
Personally, I have always been a person with broad interests in a variety of unrelated areas that I frequently nurse. But, I have no illusions about excelling and being truly proficient at more than one of those domains - maybe two someday, if I'm lucky - in a way that's useful and can make a meaningful impact on the world. I'd be the last to protest diversification for the sake of health and sanity, but it's important to realise that it's just that.
If you spent the last ten years intensely immersed in programming for most fruitful hours of your waking life, but also "occasionally" like to screw around with automobile mechanics, then it's a basically immutable fact that you're going to be an eminently better programmer than an auto mechanic. And while it may be fun and valuable to exercise your mind in both areas, the auto mechanic side of you isn't going to get the same kind of satisfaction that comes from the efficacy and power of competence and deep, erudite knowledge. It's being able to accomplish something concrete, nontrivial and lasting that gives programmers that high, which is why so few (outside academia) write toy code just for the fun of it that nobody's ever going to use.
The point is, I think that most intelligent people want to apply their skills and capabilities in ways that have a measurable displacement in the real world. That takes so much time, effort and devotion that it leaves tragically little time for other things. And I think that's why well-meaning people end up in the "tunnel vision" of their "narrow" professional self-concept; it's a cross we bear for being really good at what we do, or striving to be.
With regard to Relay for Life, I'm going to end with a quote from Dmitry Orlov's essay, "Thriving in the Age of Collapse," which is otherwise on the wholly different topic of his very pessimistic views of energy consumption sustainability. (http://nosedive.org/backup/orlov.htm)
I think it sums up my view of the usefulness of participating in such things, though:
"Am I being overly optimistic about the promise of a reformed American suburbia? Some people are ready to declare suburbia to be at an end. But then I know that Americans are very much driven to hyperbole, always willing to put an end to something certifiably unstoppable (war, AIDS, cancer, poverty, global warming), usually by making a small charitable donation, by wearing a colorful plastic bracelet, or by going for a walk, a run, or a bicycle ride. Below the charming, childlike confidence and optimism of such ventures lurks a culturally ingrained inability to grasp something basic: not all problems are solvable.
And thus I discern an element of wishful thinking in the idea that suburbia is going to conveniently disappear, and that everyone who lives there will simply go and live someplace else. A cabin in the woods, perhaps? Or a picturesque desert island? How about a space colony? Nor do I find it plausible that half the U.S. population will lay down and die shortly after they discover that some of their cars no longer run or that their kitchen appliances no longer work. And so I find it safe to think that most of the existing infestations of Suburbia americans are ineradicable, but that the evolutionary pressure of a chronic energy shortage will force them to evolve into something much less energy-intensive. Whether, in each case, that something will turn out to be absolutely horrible, or quite pleasant, will depend on many things."