Most people move their desktop as often as they move the rest of their furniture. For college students who dorm, there are small form factor cases that can still support full size GPUs and CPUs.
I know this because I own a SilverStone FTZ01 [1] and have tried to take it with me on a flight back home in May, but ended up giving up on it because it was simply too difficult to adequately protect in a luggage without going over weight limits.
A much smaller chassis with just a discrete GPU + power supply probably won't have this problem, and as a result, for my use case at least, it would be a much more practical option.