There should be new content as well, but I think repurposing content is very helpful for content creators. It gives them more time so that they can focus on other aspects of content creation like learning new things and improving the business side of things.

Also, as liberosist mentioned, sometimes you put in a lot of work in an article and want it to have the maximum impact. So reposting on different platforms helps you reach the most amount of people and have the greatest impact. :)

But I see what you mean and agree that novelty is also important. :)