Comment 5 for bug 65587

Actually it's not the only package, I know among other things bittorrent and rsync have this option, and it's there so that avahi can be installed by default but not enabled on an ubuntu system.

Yes it is a little confusing, that is unfortunate.

As for upstart/rc?.d links, thats the price of moving forward into a better init sytsem, it's simply something people will have to learn like the various other changes I guess

As for a warning, see https://launchpad.net/distros/ubuntu/+source/avahi/+bug/65603