The substrate method has been around a long time and I bet you that even the big breeders learned with that method. It has worked for years and most people go by the quote "if it aint broke, don't fix it". A new substrate-less method will mean having to change a lot of things especially big breeders, not to mention that the big breeders clutches are usually pretty high dollar and they probably wouldnt want to take a chance on a new method. Also, someone mentioned drowning, thats something to worry about and can be avoided, however it would probably take some rigging of a tub etc, that would take a lot of time for the "big breeders".