they take a bit of setup, there is a cost factor, but also they need to be "load bearing" which is substantially different from just sticking a tent in a room, or whatever... even those spinner style ones take about 500# weight factor so then you're talking about bolts and joists and beams and the like... they also can be mechanically complex which is not something everyone wants in their grow... hell i know some folks who still hand water every plant every day... to each their own...