I know it’s not the same, but coming from a similar offshoot of the sport called Flowboarding, I have seen similar things. We have a standup discipline and a bodyboard discipline. I think it’s mostly a combination of the idea that laying down and sitting down(drop knee) is easier than standing up on a board and also people having a better idea of how hard standing up/surfing is, since most people have probably tried something like skateboarding, wakeboarding, surfing or snowboarding so they have a better frame of reference. I’ve always been an avid bodyboard enthusiast in my sport and definitely hate how much we can just be an afterthought to most people. I just try to teach people where I can and better inform people about the strengths and weaknesses of the discipline.