Did we see the same movie? Roy’s wife bailed on him and took the kids with her when he went crazy. They weren’t exactly standing by him. And the kids came off as dullard brats who fancied goofy golf over a seeing a Disney film. Odds are the wife was going to want a divorce. Stay on Earth and pay alimony and child support for the next 15 years, or go with the aliens and possibly be declared legally dead? Tough choice! 😛
Contrast with Elliott, who has plenty of reasons to stay and not go with E.T. Although the feds probably followed him and his family’s every move for decades just in case E.T. ever came back.