I thought that too first, but actually they do seem quite similar. Main difference from computers point of view is that paper printers take in postscript and 3d printers take in gcode. Of course the printer itself is completely different but that is all quite opaque to the computer.
If you want to be that pedantic, there is little difference between a monitor and a printer. There are a lot of configuration differences between 3d printers and normal.
