It seems like the very old projects are very set in their ways (unsurprisingly). I complained about ImageMagick's process a while ago to no avail: http://www.imagemagick.org/discourse-server/viewtopic.php?f=...
Until pretty recently tools like git, hg, bzr didn't exist. Now one of those is looking abandoned in its own right.
Switching repos and tools isn't trivial, and really if the tool is free software and works across common OSs, I really don't see the problem. DVCS doesn't have to work for everyone.