Sure, but what if you don't need the item right away? Take the insurance broker who buys paper, toner, pens, etc. from OfficeMax: Most of the time, it's probably easier to order that merchandise online and have it delivered. It's the little guy (the home-based freelancer who wants a dozen pens that will last him two years, or the schoolteacher who wants a gluestick for a classroom project) who's more likely to come into the store.
And often, it's easier--and quicker--to order online. I live in a city, and all of the better computer and electronic stores are in the suburbs. If I want a new router, an external hard drive, or some other device, I have to find time in my schedule for a drive to the 'burbs. Or, I can order the item immediately and have it delivered before I would have been able to go shopping in person.
Obviously, some types of retail are more--or less--"touchy-feely" than others are. If you want to try something on or examine an item's looks, a brick-and-mortar store is much more convenient than online ordering. At the opposite end of the spectrum is travel, where you'll probably get a better shopping experience online (where you can see hotel pictures, read cruise-ship reviews, etc.) than you would while sitting next to a desk in a travel agency.