Many consumers don't want to postpone gratification and wait for a shipment. And of course, there's a wide segment of the populace who don't use computers and never will. Plus there's some people who are bored with it, or don't have the patience or initiative to use their computer. And of course a high percentage of consumer purchases are too small to be e-transactions. There are no doubt, other limitations.
Some business lend themselves more favorably than others to e-commerce.
Stock trading certainly appears to be one, but here again the commissions get lower and lower. Finally a slowdown comes and it's terminal for these price cutters. Books and music may not work. Postage expense for these e-tailers runs higher than for standard companies. That's compounded by returns and the penchant for consumers to buy things and send them back.