This highly depends. I believe what Grumple is talking about is contracted work for a specific customer that is asking you for something different, even though

This highly depends. I believe what Grumple is talking about is contracted work for a specific customer that is asking you for something different, even though what you've already delivered works. You're talking about consumer-facing product teams that make whatever they want and try to sell it after the fact, coming to their own decisions regarding what their "requirements" should be. When your work is funded by a specific customer, the requirements are whatever that customer says they are. And they're almost never going to let you change something just because you wanted to in order to learn a technology you can put on your resume.