I think it's more a logistics issue -- each dive station on BAIV has a dedicated fill whip and tank securement. Another Caribbean dive boat welcomes sidemount - AquaCat. That boat is set up with two tank holders per dive station. I find it much quicker and easier to kit up sidemount. Attach two boltsnaps per tank, and plug in the inflator hoses. The BC goes on my wetsuit hanger between dives.