That's old world thinking.
I used to buy all my Macs online. I wanted them customized and, come on, they're heavy. Why lug it to my car by myself?
But Apple's profits are shifting to iOS. I've since bought 7 iPhones, 3 iPads, and an iPod Touch in an Apple store. Why would I wait to have it shipped? It's there, just buy it!
So while the Macs I bought always used to cost more than what I spend on iPads, my personal "what I spend in the store" number has skyrocketed.
What they should do is to offer the same custom (BTO) options for both retail store pick-up/purchase versus online purchase/shipment. That essentially means that there is little cost-convenience advantage to using one versus the other. But maybe I'm just dreaming.