I spoke to someone recently about their views on submission. They stated that a sub is a sub for a reason, to learn something and to evolve into a better being. I think that is a lot of it in a nutshell. Subs need 'training' and to 'reflect' and 'guidance' and so many other things according to a lot of people. Dominants on the other hand, are not viewed as needing all of this. A lot of people seem to think Doms come in this perfect package that needs no work or instruction.
Hence the many many more discussions about subs.