That could be part of the reason.... I think other reasons include. Stupidity.
People assume ebay will have "cheap prices"
which they don't a lot of the time. sure you can find a good deal here and there but a lot of ebay members go on there thinking they're getting a deal when they're really not.
Not everyone lives near an apple store or a big mall or a CompUSA. For some ebay is there closest look to electronics.
and for that, i'm thankful.