Given that everything in life worth having requires work, why do so many people get comfortable, let themselves go and simply take their spouse for granted until it's too late?

Question.. You marry someone who is drop dead gorgeous, very in shape, works out, very fashionably dressed, applies tasteful makeup daily.. could be a lingerie model..

Fast forward ten years .. a few kids later, gained a lot of weight, doesn't work out, wears sweats around the house, flannels to bed, frumpy style, doesn't fix hair or make up anymore...

Is it okay for a husband to request that his wife take an interest in looking nice, things like wearing makeup, nice hair, wearing lingerie to bed or should he just accept that because she had his children, he should no longer expect her to take care of herself?

Is it superficial to expect your spouse to want to look their best when with you or should marriage be more comfortable, relaxing and 'accept me as I am' kind of thing? This could work both ways.. for men and women.

There are many newlyweds on this site.. just so you might relate to this question, how would you feel if soon after you are married your spouse changes completely?

Thoughts?