As has been said, risk management.
My parents used to rent one of their properties to Norwich council and every single tenant absolutely trashed the place.
The council did pay for repairs, but in the end they sold up.
However, not too long ago I did agree to someone on disability benefits to move in, but it turned out that my agent found out all kinds of things about them (presumably from references) and that they were lying about quite a bit of stuff, and that was that.
That experience (rightly or wrongly) has put me off a bit, and I guess like most landlords I just want to hedge my bets and take the safest option.
I do however sympathise with you fwiw, and it’s probably not fair to tar all with the same brush, but getting the wrong tenants is a nightmare I don’t want to think about, let alone experience.