Retailers have spent 50 years offering a wide range of options to scratch any shopping itch. They have trained consumers to expect, indeed demand, a wide range, but given their walls are not elastic, is it any wonder that that when the elastic walls of the e-tailer comes along, we do what they have trained us to do, check out all the options and buy the one that best meets our needs.
Another perspective is that retailers to date have had all the power, what got stocked had a chance of sale, so retailers charged suppliers to have their product on shelf, and charged more for the best sales positions, in effect mixing the picking of winners with extraction of cash from suppliers. Now, suppliers have another option, one where the usurious practices of bricks and mortar retailers is mitigated, and a product has the opportunity for sale on its merits, not just on the pocket size of the supplier.
Is it any wonder the shift to net shopping is gaining momentum, the retailers have only themselves to blame that they did not see the shift happening, or just wished it would go away, and failed to use their capital and position to carve out a position for themselves.