In KY, to the best of my knowledge, it isn't a requirement unless you want to sit in a chair (I'm not sure if it's all chairs, but I know that SD required it). That being said, at least in my lodge, it was expected that you take it and there was definitely a stigma for choosing not to take it.
I've told this story elsewhere, but at the time of my raising, I had a LOT going on in my life and couldn't dedicate the time to study. I had planned on coming back to it when things settled down. That being said, those chairs need to be filled, so I was forced to "give" my proficiency, which was a joke, so that I could serve. Now, obviously, I take Masonry seriously enough that I can study on my own after the fact, and I've done so, however...I've never found anyone willing to take the time with me to learn it since then. Who wants to spend months teaching something mouth to ear for a man who has been in the craft for years and who technically already holds his proficiency? This wouldn't be a huge problem with the EA or FC degrees; you can just study the monitor and it seems like lodges are putting on the degrees all the time. But the MM is different. The two monitors I have don't give everything, and the degrees are often done in a non-typical setting (i.e., outdoors, at a different lodge, etc) so they are more difficult to get to. To this day, while I consider myself well educated on the EA and FC degrees (but always still learning), I am weak in the MM degree.
Long story short, do your MM proficiency and REALLY learn it, don't just go through the motions to get the piece of paper.