I haven’t ever seen vandalism of these types of things, but I imagine it might be drug addicts or mentally unwell. It’s easy to imagine angry teens or greedy people, but given many unhoused people having schizophrenia or drug abuse, delusions could definitely lead to destruction of these public spaces. Although I only ever saw that with a store front, not a free service thing.

Still infuriating though, people need treatment and society does its best to ignore that or even discourage it.