That's a factor, but I think an even bigger set of factors is:
(1) industry-focussed venture capital and related support infrastructure (particularly for startups) prefers proximity,
(2) there are benefits to proximity to other firms in the industry other than capital and support structures, e.g., it's easier to pick up experienced workers as you expand if you don't have to get them to relocate,
(3) With the money flowing into the industry, wherever it is concentrated is going to become expensive, because the number of dollars chasing housing and other goods is going to be high compared to places it isn't concentrated.
They save a significant amount of it, more than they would have saved in any other place. And they can leave at anytime to a low-COL place and buy a house in cash.
160K salary in SF is probably equivalent to 75K in the middle of America? (considering food, rent/car/health expenses)
It's not a delusion. Sure, if you find the culture, entertainment, and other lifestyle features of Denver, Austin, San Diego, or Atlanta an acceptable substitute for NYC or SF Bay Area lifestyle, you can get that substitute a bit cheaper. Not everyone does (if they did, Bay Area and NYC prices would drop and those other places would climb.)
“Overrated” just means other people value it more than you do. But you should be happy, because that presents an opportunity you can exploit by satisfying your preferences more cheaply elsewhere.
As an industry, tech skews young. And a lot of young people want to live in urban environments full of culture and entertainment, and have a job that has a social dimension to it.
Now that I'm older (thirties, married, kids) remote work from somewhere other than NYC seems appealing. But it didn't a few years ago.