Seems like a reasonable business decision to me.
Seeing as it's a mega-corporate chain, they likely have a high employee turnover rate. Could you imagine having to train or find people who know the difference between the plethora of AK or AR variants, random accessories, or, say, all the possible trigger/safety/decocker combinations in Sig's pistol line? It's hard enough to find knowledgeable help at dedicated gun shops sometimes. Would probably be even worse if you throw in a recent high school graduate working at the mall over the summer to save a few bucks before shipping off to college. With a limited selection of Fudd guns with pretty standard options, there's a whole lot less merchandise to train people on.
Not to mention all the laws the buyers/warehouse people would have to keep track of when sending stuff to all the stores. Bolt and pump guns are almost universally legal.
On top of that, they'd need to make the hunting sections a lot bigger in order to keep a large enough selection in stock to satisfy everyone. Not only would this compound the problems above, but if they started selling handguns and/or black rifles, they'd surely have to deal with more harassment by pedantic ATF inspectors.
Granted, one could argue they should join us in the fight against the latter lest we all hang separately. But, on the other hand, think of all the people shopping for other things there that might get involved with shooting sports who otherwise wouldn't have. While it may seem bland and uninteresting to most of us, the sanitized, retail atmosphere is probably a bit less intimidating to most fence-sitters than a traditional guns shop stocked with black rifles and where every employee is carrying.
And even if a small percentage of suburbanites who pick up a pretty bolt gun later go on to buy more stuff elsewhere and/or join the NRA or something, it's still a net gain for the cause.