I'll counter with a family anecdote. My sister and her husband own a rental home in the DC suburbs. It's within easy commute of the Pentagon and another army base. They've been able to rent exclusively to officers or senior enlisted. Price-wise, the army housing allowance is at the top of the market of the size/style of home (mid-sized 3-bed townhome). The tenants are mostly price insensitive - as long as the house is priced within their allowance and meets their needs. Their theory is a career military tenant more likely to be a good tenant than some random person. So far it's held true, but small sample size (10 years of rentals, 4 or 5 tenants).
Anyway, point being, this is like any other investment, you have to do the work up front to ensure the risk and payout are balanced. In their case, it was a no-brainer to keep the house when they moved into something larger. Almost zero chance of the home being unoccupied, better than average chance at a good tenant, etc. But, they're also financial well-off and could afford to keep a relatively expensive house in a nice area - obviously not an option for many in the middle-class.
Anyway, point being, this is like any other investment, you have to do the work up front to ensure the risk and payout are balanced. In their case, it was a no-brainer to keep the house when they moved into something larger. Almost zero chance of the home being unoccupied, better than average chance at a good tenant, etc. But, they're also financial well-off and could afford to keep a relatively expensive house in a nice area - obviously not an option for many in the middle-class.