Because they don't practice it.

Seriously, people devote so much time to becoming good at "structured thinking" that they spend less time talking to others, or doing big-picture decision making (the last one is easy - just start making decisions and facing the consequences of your terrible decisions, you'll get better).

Literally everything in the world can be solved through practice. (That's clearly an exaggeration, but its true enough).

I definitely don't think that "programmers" (whatever they are) are any worse at other things by virtue of their talents. They are less good at other things because they have not practiced those things.

I would say it is the other way around: People who are poor at social interaction avoid it, some of those discover programming, and because they spend less time socializing they have more time to practice programming. So in my opinion it is not “Has structured thinking which causes poor social interactions” but “Has poor social interactions, retreats and learns structured thinking”.

You are painting with pretty broad strokes there huh? Not everyone is a stereotype in a tv show.