I personally shop online for two main reasons: selection and price. Think about it...how many stores do you have to personally visit (drive to, park, walk inside, find the right isle/dept) in order to see the thousands of fashion styles, jewelry or anything else you're in the market for, that are available with a few simple Internet searches and mouse clicks?
The other factor is price. When you shop at a brick and mortar store, with each purchase you are partially paying for their rent, utilities, salespeople and the rest of the overhead that comes with a physical location. Online stores generally have a warehouse in a remote location and a call center, that's it!
For me these two factors are essential and keep me shopping online :-)