I suspect we will see startup founders trending older if it isn't already happening. Companies stuck in the old way of thinking that older is slower will probably be disrupted in the next recession.
Over 50 seeker here (25+ years experience, first IC then mgmt). All of hiring managers I've dealt with this time around are at least 10 years my junior, and they disagree with you. They view me as a risk (higher compensation, less "hungry", higher "flight risk") and prefer people their age or younger. Don't call it ageism though, that's just how the world works :(
Speaking only for myself, I would have been fine, taking a lower salary, if the work (and work environment) were interesting to me.
I also would not have been interested in flitting around, looking for pay bumps. I was already set.
In fact, I suspect that someone like me (and I am sure there are many others, much like me, and likely, far more qualified), could be an absolute Godsend to a startup.
I don't think most companies behave this way. Maybe at one point they did, but I find the reward for doing great work is "That's why we hired you"
Yeah maybe you get a yearly raise and a bonus but it never is big enough to make up for taking a lower salary
Anecdotally, I think it already is. Part of it is simply because the younger you are, the less risk you can take with the cost of housing the way that it is. Older people/Millenials often have housing security and can take more risks this way, plus the other factors you raised.
Can't speak to whether that's universally true, but it's something I've been seeing: including people in their late 30s to mid 40s leaving cushy well paying corporate jobs to try founder life: they have big nest eggs from said previous jobs, so why not!
If you see more older people starting companies it's because we can't find employment and have to find a way to be productive somehow...
The fact is that there's nothing unique about any age group, and the only difference between them is their birth dates. Intragenerational differences are always larger than intergenerational differences. In any age group, there are varying degrees of competence, varying degrees of attitude, varying degrees of personal circumstances (e.g., home, family).
Ageism is treating a person solely as member of a group rather than as an individual. You simply can't accurately generalize based on a job candidate's age. Anyone who claims, "In my experience [members of age group] are mostly like this..." is putting forth weak anecdotal data that is practically useless and totally unscientific.
The paragon is talent plus experience plus willingness to learn from experience. Admittedly, more older devs than younger devs will have this combination, but "social promotion" is no guarantee of success.