Laser printers are big and clunky, and require plenty of upkeep. It's such an inelegant process, too. Use a laser to discharge an image in the drum, then use the drum to charge the paper, then pick up toner, then fuse...what if we could skip all but one of these steps?
Simply use a laser. Make
it a big one, and directly etch an image into the paper. Do away with the drum, fuser, high voltage, and all the messy toner. Solid state lasers are cheap and powerful enough to precisely scorch the paper, and the whole system has no consumables. If faster printing is desired, simply use a bigger laser.
Of course, to use any old paper, some calibration is required. When starting a different type of paper, the laser scorches a gradient across the top of the page. A rudimentary scanner then analyzes the mark, setting power levels for greyscale images. The mark will be rather small, but subsequent pages may forgo calibration for tidiness.
Now laser printers can be lighter and cheaper than inkjets, and cost only electricity to print.