This post points to perverse economic incentives as being one possible cause, but I have also seen this happen in open-source projects. It's a matter of listening to the wrong people, in my view. User feedback is incredibly valuable, but when user feedback comes in the form of GitHub issues rather than careful testing and conversation, the team will inevitably find themselves building more and more and more for no real benefit.
I've quoted this before, but what Don Norman says in The Invisible Computer still applies:
"Don’t ask people what they want. Watch them and figure out their needs. If you ask, people usually focus on what they have and ask for it to be better: cheaper, faster, smaller. A good observer might discover that the task is unnecessary, that it is possible to restructure things or provide a new technology that eliminates the painstaking parts of their procedures. If you just follow what people ask for, you could end up making their lives even more complicated."