You notice after a while that the Pattersons don't really expect all that much of Michael. They've come to expect him to make a token effort to do things most people would without asking and no more. The odd occasions when he does act as if he's appreciative of those around him are regarded as rare miracles. "Hurray! Mike did housework without being told to. Woo-hoo! He paid back a loan! Whooty-doo, world! He picked us up at the airport!" Why is he allowed to slide on by doing as little as possible? Because he's been doing it all his life. How did he get that way? Elly let him. When firmness was called for, she started to buckle which made our 'hero' realize that if he pushed hard enough, he wouldn't have to do what other people told him to do. When you combine that with Elly's tendency to angrily declare defeat and John's will to escape from unpleasantness, it's not hard to see that they gave up on trying to change him after a while. They were reduced to shipping him out to the farm and other non-solutions to manage his asshattery because correcting it was beyond them. Simply put, the people around him are at pains to minimize the damage he does.