Historically, and if we're talking about someone with 30 years programming experience, this history is very relevant - programming has been a popular field for smart but antisocial/unsocialized nerds who had very few if any friends growing up and have spent much of their life alone at a computer.

For a person with that background, simply sharing a relatively small private room with a total stranger can be overwhelming. It doesn't matter what trivial test you're giving them, if they're not able to think. The test is failing to actually determine if the person can do the technical part of the job, instead it's testing how the person performs in close quarters shared with unfamiliar people.

The whole giving homework for technical vetting is a great way to get around this class of problems.

But what if you're looking to hire people who go outside sometimes and can talk to people and can write code too? Or should that be illegal?

It's not like you forego the in-person interview and don't learn what you can from that. The point is, by including a take-home portion of the technical interview you can get a better sense of the individual's technical abilities.

If, in addition to what seems to be a technically competent individual, you find they don't perform well in-person, then you take that data and weigh it against where your priorities lie for the position.

There's a huge difference in knowing "technically great, performs poorly with an audience" vs. "technically poor, but we only tested them with an audience".

Furthermore, it's not uncommon for people who experience anxiety during the in-person to loosen up as they acclimate to the office environment and their peers. These people can actually be some of the best contributors, and it can be a very costly mistake to misjudge them. This personality type tends to be quite loyal and averse to changing positions, because the whole process of interviewing and acclimating to a new environment is so stressful to them.

You seem to have a chip on your shoulder in this discussion, are you having a bad day?

Not at all, I'm enjoying myself and the debate (while finding it kafkaesque that people are finding ways to defend failing fizzbuzz on an interview). How are you doing today? That might be the only legitimate point I've read in this chain so far - if you hire people too socially impaired to write fizzbuzz, they'll be less likely to job hop.

Now we're tacking on an additional aspect of the job that we didn't know about before. If the job requires a social interaction with people outside of the company then, of course, it becomes a factor. Let's not be silly in an effort to just be right and prove someone else wrong.

They should if they want those people, if not then don't. But if you don't, you shouldn't also complain there's a shortage of skilled people.