Why does Harry need glasses?

Some things cannot be fixed with magic (point in case: Dumbledore's hand and, I'm assuming, Moody's various injuries). Since James also wore glasses, I'm assuming his need for them is hereditary. Perhaps magic can't fix something like that.

Also, Harry never really cared either way about wearing glasses, so why would he even look into trying to fix it?

I guess it just wasn't one of Harry's main problems. We never really see him unhappy about it, well maybe except in the third book where he has to play Quiddich in the pouring rain. And besides, he looks wicked with those glasses.

He doesn't really need glasses, its all to disguise his dirty little habit. They are special x-ray vision glasses that enable him to perv on all the girls at Hogwarts.

The whole Harry Potter series is about Harry Potter attending a school to learn magic. Like everything you have to learn magic, too, and at Hogwarts they don't teach you magic medicine. Just like to become an Auror, you also have to attend additional education to become a wizarding healer. One like those we have seen at St. Mungo's. There'd be absolutely no need for a St. Mungo, either mais for Hogwarts itself, if every wizard could perform every kind of magic just out of instinct. Like Muggles, they go to the doc's if they've got a problem, the go to Diagon Alley if they need clothes. They can't charm everything for themselves, otherwise there'd not be a wizarding community at all, after all they could all take care of themselves. Who would that help? Not Voldemort, not the publishers, not JK, and most definitely not us either. If Harry goes into Gringotts, takes a couple hundred galleons out and seeks out a good optician at St. Mungo's, his vision will be happily fixed.

It gives him a quirk that is needed to balance out the perfection that the Wizarding World believes him to be.

well, there are some things magic cant fix, right?

Because, Harry's glasses were something he was born with. Plus, as someone said earlier, I'm assuming it's hereditary as James Potter had glasses as well. PLUS, some things just cannot be cured por magic.