It's kinda ironic to know that some people are oblivious as to why their adult kids won't visit them more often. They get upset 'coz of this, even though from my eyes it's very clear why the kids are reluctant to visit them. It's maybe because the atmosphere in the house isn't really inviting for the adult kids to WANT to visit them often. Or maybe the parents are too involved in the kids' lives (whenever they meet, the kids are always told what to do with certain areas in life, etc.). Or the parent keeps on yapping whenever they meet or there can be many numerous other reasons.
In the end, unfortunately, the vicious cycle continues...the upset parent (or parents) complains when the adult kids do visit and says something like this, "Ah, we've got a long lost visitor (insinuating that now they've become "strangers", so to speak)." After hearing that over and over again, the kids feel less and less desire to visit the parents...and it only gets worse and worse.
It's human nature, I guess. It's MUCH easier to put the blame on someone else rather than look in the mirror at yourself and see what's wrong with yourself that may be causing the distance between you and your own kids.