You aren't literally banished. What happens is that if you can't succeed at a high enough level, then you won't be able to afford to live in the same type of community as an adult. Economic banishment, not social, although the social separation happens as a knock-on effect. As social/tribal creatures this is absolutely a huge deal psychologically.
I think this is the root of it. The high cost of living (high property values, high taxes, high regulation around inputs like fuel and wages) mean that being able to put four walls around a family and feel even a modicum of financial security requires a staggering -- a simply staggering -- income.
If one looks at the inputs into the cost-of-living issue, I suspect one would actually find that much of the pressure cooker atmosphere is the result of bad policy. There's no shortage of land, energy, labor, or even water* in Silicon Valley. But there's an enforced shortage of these things, and the resulting high prices create the "banishment effect" for these children.
