Programs that have 'creator' features usually have different levels, there's often (but not always) a 'free' but limited account and a full 'creator' account that allows full access to the system in terms of what you can upload, and yes that's usually fee based (either subs or one off). If you go the paid route then you're usually looking at content creation more seriously (certainly with 'sub' based programs where one needs to justify investments) and as such it's often regarded as a business venture because you can in fact make cash off your efforts - it's not easy (and it won't make you a millionaire) but it can be done. Creating is then treated as a business rather than just a one off thing - which is what most people do, they make the odd item here or there.
Payment also acts as a deliberate barrier in the sense that it's a sort of quality control device, only people that are relatively 'serious' about making content will sub up and commit, which tends to benefit the business model used by the service providers (Frenzoo, IMVU et-al).
And yes, I've already made some 'bunnies'! lol