I don't mean to be snarky or anything, but.. yet you played with a guild demanded you have them? Why else would they "require" them unless people who would be a big part of your time with that guild believed 'add-ins are required to perform'?
Just the idea of a Free Company having demands like that makes me feel uncomfortable. I mean, not least because of the privacy issues around players being able to run checks on my client.. Even if it is only to look for certain add-ons, it seems pretty rude.
Still, I doubt I'll be using them to any great extent, especially given I prefer my UI be as spartan as possible. Anyone demands I operate them probably isn't someone I want anything to do with anyway.