Most of the people protesting technology putting people out of work do so because they know the same people saving big with the tech will fight tooth and nail to make sure we do NOT adapt the economy. They want the displaced to go die quietly somewhere that is not in their back yard. Unless/until that changes, every displaced worker brings us that much closer to an ugly social uprising.
We need to look at UNDER employment as well. Especially on the west coast, a number of the homeless are, in-fact, employed. Some full time. But because our job market is ruled by supply and demand (rather than needs), a glut in supply has resulted in employed people that can't even afford a shitty apartment.
Many of the homeless I see are doing the "thorazine shuffle", a gait that comes from years of treatment with major tranquilizers/antipsychotics. So for those, mental health issues is a good bet.