You have to continue to look nice or your partner might leave you.

Fashion is something used to attract initial attention. I think a lot of people don't care if their mate is fashionable after they're married? (Honestly, most men don't care much if their woman is fashionable, ever; so my perspective is skewed.)

I've had the experience several times that girlfriends pressured me to do things that would make me less attractive. Perhaps this was done unconsciously to reduce my opportunities.