Sorry, but it can be required in some cases.
I had (still have, actually) a student who was a typical vacation, warm water resort diver who had never done a single specialty, including nitrox. He is a scientist, and he wanted to do some dives in a national park related to the studies he was doing there. The park told him he could only do it if he had master scuba diver certification. We worked on that, making sure he had 5 good and useful specialties. We did nitrox (which he needed for his work), TecReational Diver (similar to GUE Fundamentals), Advanced Diver Planning (a very through look at everything you need to know to plan and execute dives in any setting), Deep Diver, Dry Suit (the lake temperatures were below 40° F), and a couple of others, so he had more than enough. Once he had that certification, he was allowed to do his diving. More importantly, he was now a totally different diver from what he was before that. In his case, it was a very worthwhile pursuit.
On the other hand, I am an instructor for two different agencies (PADI and TDI), and I am certified for both Advanced Trimix and cave diving. I do not, however, have the Master Scuba Diver certification.
OK, but that is an arbitrary requirement made by a group that doesn't know anything about diving. The MSD is a worthless piece of paper, except for those who want to collect cards.
In his case, the specialty courses were worthwhile. The MSD, in and of itself, remains useless.