I genuinely wonder if people realize how many projects get abandoned because the readership "wasn't there", when in reality, the readership just stayed silent. It's a big thing in trad pub that book series get discontinued because readers pirate the books or wait until the series is finished to buy a copy, leading the publisher to think that nobody actually wants the book enough to continue the series, but it happens with indie creators too.
I've discontinued a lot of free, online series because it's not worth putting 3-5 hours a week into posting a project for no readers. Sometimes I finish the series for me but just never post it again, other times I don't finish it at all because it feels more worthwhile to put my time into other things. Sometimes I hear from readers who are sad or upset that I didn't finish something they were liking, but the *reason* it never got finished is because I didn't know anyone liked it. If you like something, tell the creator, tell your friends, make some noise about it. If you would be sad if a story never finished, make that interest known because one of my biggest considerations before discontinuing a series is "will people miss this? Will I be letting people down" and 9/10 times, I come to the conclusion of "no, it doesn't even seem like anyone's reading this" only to learn after I've moved on that apparently someone was.