It's important to remember that. It forces the hardware vendors to stay on "their side of the line" -- or at least to give up control over any part of their product which extends into the software space. This is why it's much more important for the hardware-touching parts of the stack (Linux, GRUB, GCC) to be copyleft than the rest of the software we use.

A lot of the anti-copyleft people think only in terms of software-company/software-company interactions.