Profile of MMM in the New Yorker:
http://www.newyorker.com/magazine/2016/02/29/mr-money-mustache-the-frugal-guru
This NewYorker piece provides interesting perspective on the guy. I understand his thought process around frugality and it resonates with me. I was like that when I was younger. But to me the point of money is to trade it in for life enjoyment. To me frugality is a means to an end.... the article says he makes $400K a year from his blog now and yet he doesn't seem willing to make any changes or compromises in any way. That personality seems a bit on the obsessive side. If his wife is completely aligned with those beliefs and practices, then great! Otherwise seems like it wouldn't be much fun to share a house with him. Maybe it is partly for show now to maintain the personality cult that has developed around him from the blog.
If you read his stuff, you'll find out that he does exactly what he wants to do (works only on what interests him, takes vacations and travels for as long as he wants, designed his own house to his specifications, spends tons of time with his kid, has lots of time to socialize with his friends, etc). He doesn't feel like spending more would make him happier, so he doesn't. I think the idea of donating that money to charity probably makes him happier than spending it, kind of like Buffett in miniature.
If you optimize for happiness and freedom, then spending more isn't necessarily a way to get there. For some people, maybe, but not everyone. For many, spending more means less freedom and more stress, not more happiness.