Saw this article elsewhere, the answer is they don't need to sell. They will either reverse mortgage and the bank will take possession at the end, or they will rent out and downsize. They are generally sitting on 100-200% gains, there is no overwhelming need to sell.
Couple of well-to-do fucks passed away in my neighborhood recently, the children decided rather than selling, they'd rent it out. Some poor schmuck now has to pay $5K/month in rent to some children who didn't do anything to earn the home.
Which reminds me, my area is becoming primarily renters now. Time to get out. Good thing I bought my house 20 years ago eh.