lol Because it feels like cheating. 
The comic I work on every week takes between five and eight hours to do, but these little goof-off things take maybe, like, an hour? Since in my head these weird ghost/demon things are only semi-corporeal I get to make them sketchy and dirty. I was able to do two of them in one day. Buuuut I've already had multiple people ask me if I was going to make it a regular thing, and if they don't take much time or effort... ehhhh... I'll think about it. 
