what did marriage do

I've noticed a somewhat disturbing trend and a somewhat comforting trend in people I know after they get married. I guess the two trends offset each other and everyone is happy. Alot of my friends/most of my friends are married and some of them seem to become more responsible people while the others seem to become less responsible people. What I mean by that is some of them do what is normal for married couples to do, take on the added responsibility and do right with it, making the sacrifices that they are obligated to do when they take that step. And the other group seems like they had parents who made rules that the kids did not like and now, after marriage, they are finally free and they act like the kid that is on vacation, with no rules. To each his own I guess.