Lock-in, usually. Using a tool that has it as a dependency. Also, if it's un-useful, they probably won't be using it for much longer since it will likely be for

Lock-in, usually. Using a tool that has it as a dependency. Also, if it's un-useful, they probably won't be using it for much longer since it will likely be forked. But that takes effort, so it's easier to ask for the original dependency to just be updated, especially if the patch has already been submitted (which is like 90%+ of the work).