In my opinion, they should be more popular ...and I think Browning gives you a lot of gun for the money /with a quality action and pump gun that is at least equivalent, if not better, than the Rem 870 Wingmaster.
Price is a big deal ....and I think Browning has the BPS priced correctly for what it is.....but it'll never be cheaper than the entry level Mossberg or Remington pump guns.
If for some reason, you're a guy that wants to hang everything off your shotgun - trying to make it into a swiss army knife - then the number of options are not there for the BPS ...like they are for the Mossberg and 870's...but to me, that's a different customer than someone looking for a quality "field gun".
I think the BPS ....in the Hunter model...in a 26" or 28" barrel....makes a great gift as a first shotgun to a 16 yr old ...as they get into shooting clay targets or in hunting live birds / and its a gun they'll probably have for 2 or 3 generations....
I still have a pair of BPS models, I purchased in the mid 80's I think ...both Hunter models at that time ....and one in 12ga and one in 20ga. They'll be passed down to one of my adult kids ...or maybe one of the grandkids....
But everyone should buy what they want / shoot what they want..