We can have horses without open worlds

yes we can. there is literally zero reason why world has to be open for that o_O

heck you don't really even have horses running around like in ts3 in real life anyway

so it makes more sense if they are tied to lot and lots surroundings and if sims take them with them any lot of choice obviously they can ride them on that lot and that lots surroundings

though i really hope they don't let walkbys and such ride horses around the way they do bikes cause man... i didn't even think everyone should have bike by default but if u make it a horse.... that'd be a mess...