The economic incentive is increased business. Amazon may not need the business, which is up to them, but "service" is pretty much the only difference between Home Depot and Lowe's, as far as I have been able to tell, to provide one example.
Sorry about going off topic, but I'm curious. Wuhich of Home Depot and Lowe's do you feel has better service? I've never considered either for their service as my local Home Depot and Lowe's have equally poor customer service. The locally owned stores are the only places to get service for hardware stores near me.
And that might be a compelling argument if there was a competitor to Amazon who offered the same value proposition plus better service as a differentiator.
In this case, I don't think there's really anywhere obvious for the traffic to go, so the "increased business" is fairly minimal.
