It's not an attractive way to raise the issue, but it's true: artists should be rewarded for their work. Look at how the studios screwed the Gilligan's Island people, who languished in poverty after the networks ran episodes for decades.
No, they shouldn't. In case you haven't noticed, we have a vast oversupply of artists even at their current low levels of remuneration.
On the other hand, we have a shortage of capital available to produce/support the production of art.
Looking further at your example of the Gilligan's island actors - they didn't finance the show, they didn't screen it, they provided none of the infrastructure. If they'd told the networks to fuck off and tried to make something in their basement they'd have failed utterly. The networks could have found other people to star easily. I have no idea why we should care that readily replaceable actors languish in poverty after they've finished doing the work they were paid for.
Finally, paying artists for work they've long since finished provides little encouragement for them to produce new work (and in fact may discourage them since they can keep food on the table without producing anything new).