SO many reasons.
Price
you can check out everyones website before you buy to make sure you are getting the best price
Research
You can research the heck out of an item, look at reviews, and once you've decided, you're golden!
Self Gifting
Who doesn't like getting presents in the mail! It could be Christmas all the time!
Convenience
Never have to even leave the couch for weeks on end......not really a pro iguess
ANYWAYS after all that, there's some things I would never buy online, clothing is one of them. Too personal, need to feel good in something before I buy
U know??