My logic is mostly that we're on a site which is targeted at people who're in a fairly high-earning profession, with the added bonus of it being a fairly change-friendly profession.
If you're making Silicon Valley engineer money, whether you buy a new flagship phone every year is pretty much a matter of whether you want to, without money being a strong factor.
Its true we could buy new phones yearly if we wanted to, but in my experience Engineering types are far less interested in social signaling / conspicuous consumption and far more likely to buy something based purely on the spec sheet. You have to do more than color your phone pink to convince us to upgrade. We know how that sausage is made.
Both of our narratives are plausible. The only way to settle this is with data.
If you're making Silicon Valley engineer money, whether you buy a new flagship phone every year is pretty much a matter of whether you want to, without money being a strong factor.