I believe that spouses change after marriage. Couples who are married and are no longer dating and trying to impress each other. They get the real deal once they are married. People change because they are now living with another person, and they have to adapt to that person's habits, routines and social calendars.
People are constantly changing. So it is only natural to expect that spouses change after marriage. People also tend to relax the more time they spend with others and the better they get to know them. Spouses live together and have very intimate relations. This may speed inevitable changes that happen as people mature.