Blororis summed it up perfectly. Personally I use my plot as a sort of home base. It's where you can have your own little slice of the server. I find it's nice to just sort of make your own: decorate how you see fit (within the rules of course), enjoy the fruits of all your labour in the mines. I spend hours working on other people's plots to make them look as good as I can, just because something is supposed to be functional doesn't mean it shouldn't be beautiful too.
This reply is a bit late, sorry! Bloro and Hapy's responses are perfect. Plots are meant to help make money in other ways besides mining. Or, you can just build as you please! Personally, I have a cactus farm, iron golem grinder, and a mob grinder on my Atlas plot. If you ever want to check them out, do /p v tinyGardevoir! I can also teach you to build your own farms and grinders.