Why don't more people just live in RVs/vans? Taking out a mortgage is a huge risk over 30 years - what happens if you lose your job and cannot find another one

Why don't more people just live in RVs/vans? Taking out a mortgage is a huge risk over 30 years - what happens if you lose your job and cannot find another one at the same pay? Or you get sick and cannot work? I guess you could sell and take the equity out of the house but you lose so much money and time to the banks.