I think perhaps it's just your local branch, Brian. My local Waterstones has a FAB SFF section, but then several of the staff are massive fans. Not just bestsellers (or I wouldn't be in there!). They also do great displays (Angry Robot one month, great UF the next etc etc)
Next town over, there are two Waterstones (within a few hundred yards of each other too!). One has a much bigger SFF section than the other, because, as they told me, they tend to specialise. So teh bigger shop only has the basics of SFF, but a huge general fiction section, but the smaller one has a really great selection of SFF
In the end, it's always going to come down to the individual staff/manager. If the manager thinks SFF is just for teenage boys into D&D and that lit fiction is where it's at, it's going to reflect in what s/he orders in.