Depends on the context/language I think. Splitting a block of code into a function gives it a greppable name that (ideally) succinctly describes the point of the block. You can have that block just headed by a comment inline to try and do the same thing, but comments are extremely prone to getting ignored and left to grow outdated when the purpose of the code around them changes. It's easier for the reader to just mentally abstract away that block if it's separated into a function. And if that block is worth testing, it's much easier to do when it's isolated into its own function.

There's reasons to keep the block inline too--like if you're working in a more resource constrained environment, or if the block isn't really isolated/self-contained enough to cleanly abstract away, or if the block in question isn't really doing anything substantial. But I wouldn't say that you should only abstract away code into functions to save yourself from literally copy/pasting the lines in multiple places.