These are objects from a time when people were willing to watch machines work, not just get instant output.
Today, even if small DIY plotters were cheap to build, they’d mostly live in the “art / hobby” space: most users won’t wait several minutes for a page when a laser printer does it in seconds.
That said, it would be great if a simple, well-documented DIY standard (protocol + format) emerged that hobby plotters could implement and that common tools (Inkscape, CAD, etc.) could support out of the box.