I don't understand why you think Jon tried to work on it. What makes you think he did?
A book tour doesn't last forever, it is a few months--even if it is 6 months, so what big deal. It isn't like this was what life was going to be day in and day for this man. And he was also reaping the benefits of the $$ rewards for the book selling.
Ok, he doesn't like staying at home with the kids. Fine. When Kate comes off the book tour then go get yourself a job and go to work everyday. You go to work, you come home and you take care of your 8 kids. That means bathing, feeding, homework, lessons, games, whatever.
That is what parents do. And when you have free time, you can ride your motorycle and play some. But you do NOT go out and hang with young women and co-eds and party. That is not what dads do. that is not what real, responsible men do.
Somehow, Jon didn't learn this life lesson. Once you are a dad and a husband, you do not "do your own thing". You have a family that depends on you for big things and little things. The daily grind. You crash at night and get up and do the same thing all over again. Is it always exciting? Heck no. Is it always fun? Heck no. Do we sometimes get bogged down by the monotany of it all? Heck yes. But it is called being a responsible parent/spouse.
At least when Kate was on the book tour she has a purpose for her absence. Jon's absences have been out having fun with young women (Utah and St Tropez).
I'm not saying Jon should not have any fun. We all should have some fun. But Jon was given trips, "field trips" and lots of fun by TLC itself. Most people do not get those types of opportunities. He really had no idea of how good he had it IMHO.