I don't think this is the reason. They want people with no families and no responsibilities because those people will move to Seattle or San Francisco and work

I don't think this is the reason. They want people with no families and no responsibilities because those people will move to Seattle or San Francisco and work 100 hour weeks without having to worry about uprooting spouse and kids and ruining all human relationships. I actually hope one of the outcomes of post-pandemic normalization of remote work is less tacit age discrimination from companies that used to greatly prefer people willing to relocate.