They could certainly insist on that. The company would likely charge more in some cases because they'd know they could not recoup anything from selling whatever to others. With copyrights, sometimes you can say "ok, it's going to cost X", knowing that you can sell the exact same thing to others at X or close to it. Without that, you have to make all your money from the first sale.

Granted, this is not true in all cases, there are exceptions, and so on, but the logic of it makes sense to me.