For a long time, I drew maps by hand because, well, that was the only option I had.
A few years ago, I started using Paint to make maps, creating grids and then dropping colors and simple icons into the grid to create 'classic' looking maps that echoed D+D modules from the 80s. I liked these quite a bit... however...
In moving back to drawing by hand, I've discovered a few things:
1. The final map feels more organic and 'lived in'. My computer maps look sterile and pre-fabricated; my hand-drawn maps look like someone actually took a pick and dug out the side of a mountain.
2. I have to think more as I draw, and this leads to better maps. As I'm drawing a twisting passage or plugging in a statue icon, I'm simultaneously thinking about who dug that passage, why that statue was erected, and building stories into the maps as I go.
3. The final maps also end up with cool little fiddly bits that the computer just wouldn't allow for without more sophisticated mapping software. I know that there's better programs that will allow me to do more, but the simplicity of Paint was one of the things that I liked best about it.
Oh, and here are two more geomorphs to get you ready for the Abyssal Labyrinth.