i've noticed that, most of the time, my villagers tend to have areas that they usually roam around more than others. they like to stay by their houses, or at least a relative closeness to their house, in my experience. every now and then they do go for strolls, though, it just isn't as common as seeing them around their home or near resident services.
i made a rock garden on the top left corner of my map, and i've only see two villagers strolling within that area in the entire time it's been there; and it's been there a
while. same with my campsite; lobo lives right beside it across a bridge, but i've seen gala stroll up to sit in my campsite area instead.
now whenever i see a villager checking out an area i've never seen them in, i get super giddy and i feel ridiculous