Because about 95% of the time, good-looking guys know they're good-looking and prance around like they're God's gift to the world...
Honestly, who would want to go out with someone like that...
..
Girls fall in love with 'normal-looking, non-wealthy' guys because they're nice/funny/smart or there is just genuine chemistry. There is no set 'amount', its just love which is something nobody has ever truly defined...

My fella is an awkward, autistic, non-wealthy dude and I love him to bits. Believe it or not, women don't size up every potential date with a checklist containing the line "[ ] Hot and/or wealthy". Honesty, self-sufficiency, confidence, and humility are some of the words on my checklist, and you'd be surprised how many other women look for the same traits...

A girl does not love a guy becuase of what he looks like...People fall in love because of their chemistry and because of people's personalities and their compatibility, not becuase of how hot they are...Also, maybe you view a guy as unattractive but the girl thinks they are the most attractive guy on the planet...I mean many people get more and more attractive when you get to knwo them better which is another case it could be...