It depends what the purpose of the DCPU is. If it's the scripting engine, well, you can easily write an aimbot in 128KiB of .pyc files and the python VM. If your only access to the world is through the DCPU, yeah, you're probably out of luck, but the second scenario makes for a much smaller and less interesting game.

It's also an obvious in-game/micropayment reward to expand the address space, somewhat analogously to the N64's memory expansion pack.