Why do wizards wear glasses anyways?

[Robert Jones]

No: HPFGUIDX 78527

I have been reading the posts about Myrtle's glasses and earlier 
ones about Harry's glasses and thought of something: why do witches 
and wizards have to wear glasses at all?  If they can correct the 
length of Hermione's teeth and regrow Harry's bones with potions, 
why can't they correct vision with potions or charms?

Boris the Bewildered (who obviously wears glasses or he wouldn't 
have noticed this)