Honestly, because she is. Guys and girls have similar psychologies. If some pretty lady that’s not your wife expresses interest in you, that will make you super happy and excited, even if you couldn’t ever reciprocate that interest.
Ditto for ladies. Whenever guys compliment them, they feel good. It’s built right into our biology. It’s just that nature and culture and society are so cruel that women have to put on makeup and stuff in order to look good for guys. Whereas just the things a guy does and the manner in which he does them are enough for girls to develop attraction for them.
Look, if you don’t trust your wife, then you have issues to work out and you need to prioritize those because lack of trust is like cancer. It will eventually overtake your marriage and ruin your life.
But for a lady to not look her best is for the rest of the world to just not respect her. You really shouldn’t begrudge your one true love that.