Agreed, there are clear advantages to giving credit when both parties are acting in good faith. There is nothing stopping me from claiming that I wrote Macbeth and asking for donations on my Patreon so that I can write Macbeth 2, save for maybe Patreon’s ToS (I haven’t read it). In the absence of all copyright law, I could do that with any work, including ones published this morning by an artist struggling to get by.