Thin client is one answer to your question. Running a shell to a server results in significantly longer endurance for a client on battery than otherwise. Not swamping your system's I/O bus is another. OS incompat. Regulatory shenanigans.

Then there's also the training angle. I've found nothing quite as tangibly gets the visceral sense of computing across like walking a junior through a "where are your bits now?" now exercise with a handful of physical boxen.