Another reason is that in order to buy something with bitcoins, you have to buy coins first.
So why buy the coins when you can buy the product you want to have directly.
Everyone has the choice which route. if one can buy a product comfortable with fiat or card, s/he can go ahead and do it. for some people though, anonymity is an issue.
i don't wanna use paypal for same reason why most people here in bticointalk don't use paypal as well.