Photoshop is a little bit more than the lazy man's paint. Paint doesn't have layers for example, which when making a coloured comic are essential.
Layers aren't essential - they're just yet another tool that makes the art process much easier & quicker. My main point is that there's nothing you can do in Photoshop that you couldn't achieve in Paint (given the time, naturally), as some given examples have proven.
Now if you were to consider a program such as Illustrator, then you'd be getting into vectors instead of pixels, which does make for a different concept - but any pixel'd screenshot of a vector drawing could be duplicated in Paint eventually.
Incidentally, does anyone know what program the author of Jerkcity uses? I have high suspicions that it must be Paint (or a similar-level program), given that the common non-background art never has smooth edges.