One thing to notice is that plenty of industries have followed this pattern until they became mature (cars, breakfast cereals, aircraft to some degree). And you see this in software: the pressure discussed is at the frothy end of the market.
> it’s a just so story commingling
Explanations:
In science and philosophy, a just-so story is an unverifiable narrative explanation for a cultural practice, a biological trait, or behavior of humans or other animals. The pejorative nature of the expression is an implicit criticism that reminds the hearer of the essentially fictional and unprovable nature of such an explanation.
com·min·gle: mix; blend
Also it's not worth it where the valley is behind the curve (e.g. engines are designed in different centers of excellence).
Even for venture-backed (intended-to-be) high-growth companies, the Bay Area is only about 50% of all US venture capital investment. And there has been some spread: in my professional lifetime the "Valley" has grown to encompass SF and parts of the East Bay. When I first started working here people lived in SF and commuted to tech jobs in MP and points south.
But some products are just so high margin (iPhones, Internet search, USB-powered vape tubes) that it's cheaper overall to be here and take advantage of the affordances available.