I've been working on a computer vision hobby project (on Raspberry Pi) and it has some servo actuators to move things around. As part of the development procedure I used it as a plotter, moving a sharpie around on a square of paper.
And I made some software that turns photos into pretty good line drawings, though my primitive home built "plotter" doesn't really have enough resolution to plot them properly (and it can't lift the pen so it has to put a line between separate objects like you have to when playing with an Etch-a-Sketch). The sketches it makes are kind of charming though.
That's what got me interested in obtaining a real plotter. They're fascinating machines but are now totally obsolete having been replaced by much faster large-format printers. It's fun to watch them plotting - in the same sort of way that it's more fun to watch a steam locomotive than an electric one.