Why a "little extra"? Because that's the right amount

Yeah, it shouldn't be a profit center, just a method to keep the capitalists in line. Their use of free software is wonderful, and we want to encourage it, not discourage it. We want them to understand that there some rules they have to follow to get access to all that great code, but that the rules aren't especially onerous and that using GPLed code isn't scary. We want them to (correctly) think that it's often a better solution than BSD or proprietary packages.

SOME of them may even turn into contributors, but getting that code into as many devices as possible is a good end in and of itself, because it usually makes devices much more hackable. It gives the free software community more control over their hardware. Even if they never contribute a line of code, they ARE contributing devices that RUN that code.