Visit from parents

My folks are both retired, but they visited at the end of July for the first time since May back when we had B's birthday gathering.
They live a few hours away. Seemed to have a good time. Not sure when I will see them next, but I doubt it will be soon. Could be said that I could visit them more, but they live in the middle of no where, which is why I left there in the first place.
Not saying I want to see my parents more, because they make for awkward conversations about how "water is wetter" than it used to be. I'm just saying that I don't understand why they don't see their grand kids more when they have free time and the means to visit.