The ability to generate a bunch of traffic that looks like it's coming from legit, every-day residential IPs is invaluable to disinformation campaigns. If they can get persistence in your network, they can toss it into a bot net which they'll sell access to on the dark web.

A sucker opens insecure services to the open internet every day, that's free real estate to bot farms. Only when the probability of finding them is low enough is it not worth the energy/network costs. I think hosting on non-standard ports is probably correlated with lowering that probability below some threshold where it becomes not worth it...don't quote me, though.

At the end of the day, the rule is not to depend on security by obscurity, but that doesn't mean never use it.