A fair point, but it's only true in isolation. If they're in competition with another equally-well-stocked chain that has floorplans, then customers might prefer to shop at the niftier, more modern place with the fun maps. Note that big department stores have always had maps available at the entrance, it's not like they're inherently opposed to the practice.
Prices will just go up a bit across all items once this available in all/most stores, and the stores will stop relying on suckering us into buying a bit more than we want in order to keep their margins up. That's the small price we'll pay for the added convenience.
A floor plan goes against the self interest of the store.