Earlier quoted context omitted.
Houses that are good for wealthy retired people are not so good for young couples raising children. In particular, the school systems that are around such homes. Location, Location, Location. Secondly: those houses have tenants. They're not sitting empty. Thirdly, for the young couple. Being tied to your parents financially basically makes them a slave-owner of you. When the parents drop by or use the yard to store p…
The houses have tenants, so they can't use them for their children? It sounds like they prioritize the income stream over their child finding a home. Yeah, it isn't fun for the people who need to relocate but that isn't some impossible hurdle.
You need a good school district if you want your child to growup smart. Retired folk having 3x homes in lower-educated areas is fine for retired folk. But that doesn't mean that those homes are immediately useful to a new family.
Building new homes (and cheaper homes) in the better school districts makes more sense overall. Some neighborhoods naturally become "retirement communities" but kind of a ghetto for education (ie: young couples try to escape those areas due to poor schooling).