* dirty
* traffic
* a great deal of self-important wannabes
* _astronomical_ cost of living compared to "less desirable" environs like Denver, Omaha, Salt Lake, Dallas, or other large mid/mountain west localities
* family unfriendliness, as the chic "millennial" crowd despises children
* bad politics that impact everyday life (gun ownership, etc.) and high tax rates
and there are many other reasons to _not_ want to be in one of those hotspots.
Surprising as it may seem to some of you, there are cool and interesting people everywhere.
(The last actually fits in (b), but for a different attitude than the others.)
And the person in question is at least of the generation, and arguably of the attitude referred to in those other than the last, so its a pretty unconvincing list of why you'd think that person wouldn't want to live there.
The subject of the article obviously was at least semi-content living in SF, as he definitely had the means to depart if he wanted to do so. My list is meant more as a general reply to "why wouldn't someone want to live in one of those places?" It may just be my background of living in several different places, but personally I have a difficult time grasping why people assume that LA, SF, NY, or Chicago are the only reasonable places to live.
And, places do not have to be dirty, crowded, or high-traffic just because a lot of people want to live there. If things are designed reasonably and the populous behaves reasonably, traffic should continue to flow, there should be adequate personal space, and thoroughfares and public places should be clean and satisfactory.
No man is an island. The people you surround yourself with matter.
I agree that dependent on the level of immersion necessary, serious improv practitioners may find places that aren't the cities you listed restrictive, but there are well-attended improv troupes in other areas.
This I agree with wholeheartedly, which is why, despite having grown up in California, I'm not currently living there and have no plans to move back in the terribly near future.
However, I think all of the other things in your list can also be found nearly everywhere. It all depends on your perspective and your desires.
For what it's worth, from someone who has a great deal of experience living in many different cities, including San Francisco, it's a perfectly serviceable place to live. It is slightly inflated at the moment due to the tech demand, but not by much; otherwise the price reflects the value.