That's the part of the argument in favor of copyright that is inherently flawed.
Doing some amount of work doesn't entitle you to anything besides whatever you've agreed to get for that work, or possession of the output, in case you did it for yourself. But that's all you're entitled to get.
Work itself doesn't have any intrinsic value, only output does. The scarcity of output is what dictates what is actually valuable.
Creative work has the characteristic of its marginal cost being very high for the first copy, but nearly zero for additional copies. That's true simply because of the nature of such work, it isn't something that is unfairly imposed upon creative workers. Whenever you choose to engage in creative work, you know that, or at least you should. And if you choose to give away the first copy for free, or very cheap, that's your prerrogative, but it doesn't inherently entitle you to anything else besides the value of that first copy.
Yes, there are laws such as copyright laws that exist to artificially inflate the value of additional copies, but they go against how things work naturally, so you shouldn't rely on them, and you certainly shouldn't base your moral compass on them.
Now, I do still prefer copyleft licenses over permissive ones for the work I choose to give away for free, but only to stop corporations from taking that work and then using copyright laws to keep it exclusive to them. Once copyright is no longer an issue, they won't be necessary anymore.
