Doesn't seem all that odd to me. If there's no interest, then no one will write a slackbuild.
MAC systems generally introduce 2 things that are an anathema to Slackers:
- Added complexity.
- System overhead (SELinux is argued to be around 5% last time I looked at it)
I'm not saying MAC security frameworks don't have their place, but I'm not convinced about their value on a Desktop/Workstation, and lets face it, most people don't even make good use of the basic permissions system they already have.