"I am not sure why boomers are still waiting to sell and downsize."

Hi, itsthis, I'll provide some clues. 

1. Change is tough.  Changing homes/locations is amongst the toughest, for many, up there with death, divorce and unemployment.  Moving somewhere else takes months--even years--to feel "settled" or "Secure"  So many of all ages avoid moving.

2. Avoiding a move is easy when there's a career or just a job at stake. Getting the same job at the same salary or better elsewhere?  This is also changing--remote work from home, in certain sectors--but not significantly yet.

3.  The move means leaving family behind.  Even hate-you-guys relatives (more common than is usually admitted!) I mean, after all, they're familiar.  Go somewhere else, maybe you got...NOBODY close by to love.  Or hate. 

4. Downsizing means selling/throwing out stuff.  Big -uh-oh!  Try it.  Amazing, our attachments to...stuff.

5. Genuinely like present locale.  Can I (insert activity) if I move?  No.  I'll pass.