How did all those whole generations of parents and grandparents lost their houses and who took those houses?
Houses weren't limited in availability, other things were the limiting factors - and sometimes "move in with" would mean moving in next door or into what were called "mother-in-law" houses.
1. Force to sell due to medicare or other end of life expenses (you can not have any assets if you need full time nursing care paid for by medicare)
2. the "Reverse mortgage" people fall for.
3. Baby Boomers, a Single Asset split 5-8 ways does not go far
4. the houses owned really were not that good. My Grandparents owned their home, bought it right after WWII, the house was a small 2 bed 1 bath they raised 4 kids in... It is still in the family but it is out-dated by modern standards.
that is 4, I am sure there are others
Young people complain how much more expensive homes are now, and then can't be bothered to accept a starter home..
"I just can't understand why I can't afford this 3,600 sq foot home near downtown Austin at age 25, life is unfair!".
The rest of your sentence doesn’t change this bit.
Tons of young people today won't even move to the valley or to another state.
I worked in car sales and basically every dealership mechanic over 28 owns a home. But tech people complain about how they can't buy one somehow.
Often it could be "afforded" by the HN-income crowd just by not buying a new car.
Similar to years past, except people are less willing to do that now.
Things like Minimum Lot size, out right restriction on size of home, and other "building codes" that have nothing to do with the safety or long term viability of a construction project
It is unlikely the development my grandparents home is in would get zoning approval should a developer seek to build a similar neighborhood today. The lots sizes would be too small, the homes would be too small, and various other things would be non-compliant with modern building codes which does not mean it would be unsafe.