Previously, AppleWorks, then Photoshop Elements (4). Now, GIMP. I also recently downloaded Inkscape, which is slooow. But then so is GIMP. Maybe that's what happens when your latest map is 4743 x 2803.

As for why... well, arguably, software is completely wasted on me. I've been drawing maps (by hand) since as long as I can remember but probably one of the formative experiences of my life was encountering the USGS 7 1/2 minute series of topographic maps around age twelve, which I became mildly obsessed with replicating. Being a complete weirdo (>.>) and not knowing anything about how to actually use raster editors I just took out the pencil and paint bucket tools and started drawing contours. With a trackpad. Thus, while I still have GIMP and Inkscape and while I have been drawing maps for a long time it's still fairly accurate to call me a newbie since I haven't seriously exploited any of those programs' full potential. Probably.