Failure of imagination. Walmart's bikes are covered up with Shimano (loooooow end) branded components.
TCS
Shows what I know, it's been a long time since I've seen a current WalMart bike up close, I have an older one in my living room that has its own proprietary stuff, "Falcon Index System" and such. Ah well. In that case, Shimano should be working with the manufacturers of WalMart bikes to improve their quality, not with Trek, etc.