Provocative poses
I've written about this exact thing in the past. I believe a lot of non-nudists are trying to prove that they are really nudists by showing all that they can. They do not really know that this does nothing to reinforce their claim that they are a nudists.
Well in my opinion which will probably bring some arguement from someone, but oh well.
I do not think most are trying to be provocative with how they are posed, I think it is all a matter of perception in who is looking at it. Sometimes people are trying to be funny or show that they are a fun person by acting crazy and they might stand in a way that appears that way to them as a "hey look at me am a fun person to hang out with".
I do not know, I could ramble on about this for a very long post, but I hope that little responce is sufficient to get a basic understanding of my opinion