For one, a PC on a stick is much lighter than a Macintosh 512k. And it has no CRT or hard drive that can be smashed during transport. You can slip it into a work backpack or briefcase - try doing that with the Macintosh.
You do have to bring your own peripherals, but being able to move your computer around previously set-up work points is already an improvement from not being able to carry it at all, or carrying around a laptop.