It's more like someone sitting on a bench you have on your front lawn. You either put it there for people to use, or you didn't intend for that to happen by have no reason for caring, or do care and will put up a fence
I have an open wifi network set up intentionally. I hate my neighbors but there is a nearby park, though I am loath to buy additional equipment to give those freeloaders a decent signal
sure, maybe the person was just too lazy to put a fence up but that doesn't change the fact that you would still be trespassing no matter how much the owner did or didn't care about people using their bench.