I have a gentleman down the street, fixed income, no kids to help him out, can't
get a car, rides bikes from the thrift shop, $10 to $30 range.

He rides very slowly, to and from the store, doctor and park but has had three
bikes develop the same problem. He is not heavy, 180 maybe.

The rear wheel gets badly warped and the crank bearings come loose.
I have fixed the crank bearing on two of the bikes several times. I do
my own repairs and have never had a problem with mine and I do 60+
miles rides on a regular basses. I have done the rear wheels several times
and he came by today with the wheel on the Schwinn Varsity completey
bent against the frame. He said it happened while he was just riding down
the street, started rubbing and then stopped altogether. None of the spokes
are broken, but the wheel has a flat spot now, about a foot long.

What am I missing here?

If I thought it was just the bikes, I would go to Wally Wally and get him a
new bike. But there is some thing else here??