It depends on a few things
-my relation to the character/person I'd be drawing for. I like to give to people I look up to and/or care about, so I Rarely draw fanart if I don't care about the source material
-It's gotta be something I feel confident in drawing. I'd rather give someone nothing than a piece that doesn't live up to expectations
-I chose to draw it. I almost never do requests, when I do it's typically me asking which of my OCs someone would want me to draw.