I like telling stories. I'm not a very good mapper, and I could never finish a multiplayer map, which is pretty much everything I ever attempted.. I'm just starting into doing a single player project, and man I'm enjoying it so much more... All that really matters in a multi map is a layout, and some purty scenery(and even that is negligable.. look at iceworld!
johnny). But with single player, its more like writing a book or a movie. I'm suprised it took me this long to get into single player because I have always been an avid writer. I love how subtle you can be with a map, you don't have to say anything, just let the scenery and gameplay tell the whole story.
The most frustrating thing about mapping is trying to get my quality standards and abilities to jive with each other. If I can't get something to look just right, I lose my drive to continue and the map usually(always actually) ends up unfinished.
And its a cheap hobby.. I mean, I paid $40 for Starcraft, HL1, and $50 for HL2... That is $90 I've invested over nearly a decade of level editing and modeling(ms3d ftw), and I run a $500 computer. Can't beat that.