As has been said already – any horses being hacked out will most likely be doing so because the yard they are on doesn’t have the facilities for in-hand or ridden work. That, and because it’s as good for a horse’s mental health as it is for ours not to be stuck in the same place the whole time. You can explain to a person why they have to limit trips out; you can’t do that with animals.
Our yard is just three (pairs) of us, so we’re scheduling it so we’re not all up at the same time, have increased the percentage of in-hand work vs. ridden work, and no jumping. Thankfully we have only six horses on seven acres and they’re all in one herd/field at the same time, which leaves the other fields to ride around if we need to let them stretch their legs. Not everyone is as fortunate as us however.
Unless you ride yourself, what looks to you like an uncontrollable wild horse isn’t always necessarily the case. Ours are all ex-racers, and can get a little lively when out as they’ve been trained that way. To the untrained eye it would definitely look dangerous when they’re jogging on the spot and bouncing up and down, but I can guarantee you that (certainly in our case) the rider isn’t about to get thrown off!
If you see horse riders out, as has been said, don’t be a dick. Slow down, give a shout before you get to them, and ask how best to come past. Keep talking so the horse recognises you as a person on a bike, not some weird brightly-coloured thing, and wish the rider a nice ride. Things are so much better when we all try to get along, especially at the moment.