Some parts of my rig are from the LDS, others were purchased used.
I'm just saying, the repeat business argument doesn't fly for me; if the LDS predicates its business on stocking your ever-increasing needs each step of the way, the worst time to lose your business would be at the high end, once you've established yourself as a repeat-customer and big spender, by sending you somewhere else when you're ready to go doubles/bpw/etc.
I'm not a crazy gear guy like many of the locals here who have redundant drysuits and can lights and 20+ tanks in the garage, but even after my main kit was purchased, assembled, and optimized, I've still given my LDS upwards of hundreds of dollars a month in miscellany that I've needed - from fills to hoses to extra parts and replacement gear.
I just don't think it reflects reality to say that shops refuse to stock bp/ws because they believe they'll lose an opportunity to charge for intermediary stuff that the bp/w renders irrelevant. A mistaken belief that "there's no profitable market" is probably more in-line with reality.