Once you go past 4 days, the price difference for each extra day is practically nothing.
So we always get passes to cover the absolute most days we might possibly think about going to a park. That way, we have the freedom to go to a park every day we are there, even if it's only for a short time. So if we decide we just want to go watch the fireworks in the park one night or run in on our departure day for an hour just to ride a favorite attraction one more time, we have that flexibility.
And we aren't hoppers. Sure, it adds a little flexibility, but for us, with small kids, the time and energy it would take to leave one park and go to another just isn't worth it. There is so much to do at each park, that it's easy to spend a whole day at each park. Even if we take an afternoon break, I've never felt the need to go to a different park in the evening instead of returning to the same one.
I can see why some people like hopping, but for us, there's really no need.