While I agree Mercurial generally is more conservative I also believe they do this because they have a well used extension system. So you can't really say they

While I agree Mercurial generally is more conservative I also believe they do this because they have a well used extension system. So you can't really say they don't support power user features when many of them are only a configuration option away. The real difference I thing is the way they manage branches, because this is part of the repository itself, thus changing it through extensions requires everybody that pulls the repository also install this extension. And if you do this then you aren't really using Mercurial or Git, you have instead created your own DVCS.