My LDS has a big plaque on the wall, and when one gets their Master Diver card, your name gets engraved on the plaque. Similar to how Colliam7 mentioned the certificates.
I was close in terms of specialties and was working on my Rescue Diver after a decade of diving. I had done specialties as I needed them for the kinds of diving that I wanted to be doing. I had not planned on bothering with the MSD card. However, my daughter (then 10 years old) was getting her O/W and basically challenged me to get my name up there because she wanted to get her name up there with mine. For her, it was a commitment to achievement and to extending her dive training.
After she was certified in 2013, she did a couple of specialties that she could do when she was still 10, then got her AOW in Bonaire last March and Rescue shortly thereafter, as well as the last couple of specialties. She set herself a goal and she achieved her goal of being a Jr Master Scuba Diver at age 13. I couldn't be prouder of her for setting a goal for herself and achieving that goal. And prouder still that she understands that she still has lots to learn!
Our names are not side by side on the LDS plaque that I mentioned, but she is now up there with me.
Everyone has their own reasons for getting the Master Diver card, or for not getting it. In my opinion, the only wrong reason to get it is any expectation that it should be the end of your own personal improvement as a diver, whether you choose to go pro or not.