Mike, good observation. For better or worse, the big 3 provide various incentives to pro shops that can't be matched by the little guys, so who gets the wall space??
It's a shame. Just take for example, Motiv. They're producing probably the most complete line of balls from any company, yet in many areas they're a rarity. The problem is that most bowlers are not enlightened enough to do their own research and try the smaller companies, and you see it on the lanes.