In the past, people used to entertain themselves more than they used to (in part because they had to, of course) -- today, everything is a commodity. If you can't sell what you do, then it has little value. Fanfic -- as a pursuit by serious people -- doesn't fit into this mode of thinking, which is why so many seem to feel the need to excuse it as merely a stepping stone to "real" authorship.

In my tiny part of the world, there's a very awkward relationship between "professional" and "amateur," in part because money has so little to do with it. Many performing artists don't make their living, or even a significant part of it, from their art, so they make their claim to professional status in other ways having to do with attitude or devotion. These qualities are much harder to quantify, so that the label "professional" is a slippery one. A colleague pointed out once that professional basketball players are much more accepting of players in a recreational league than visual artists are of what used to be called a "Sunday painter." Your comment about "entertaining ourselves" is a bit like the issue of the "Sunday painter" -- since the difference between him/her and the putative pro is so nebulous, it makes for tense relations.