Because in my game there is now the remains of a dead dragon right by the marketplace in Riften and it's kind of messy. It may not be the most picture-postcard town ever, but having this great heap of bones slap bang in the middle of it is sort of disturbing.

I suppose I can always use the command console to disable it.

Well... they disappear after a certain period of time that I am not aware of. They do disappear eventually though, maybe after you kill another dragon.

I went into a shop and came back out and it had gone - I wouldn't have minded so much but it was right across the pavement and NPCs kept walking through it!!!!

http://www.youtube.com/watch?v=WnroGuXeNmI

Easily moved!