Why does alliance faction go down?

Why does alliance faction go down on it's own? What causes it?

I Call it faction degen.
I'm not sure if its 10% of your total per day, or 1.5k per day. I'm guessing its 10% per day, as this would stop it from getting too high for uber leet alliances, allowing newer alliances to catch up.

Faction drops by 10% per day for alliances that aren't holding any towns.

It goes down because you're not doing anything to keep your guild in the spotlight. Overtime the factions forget about joes guild because joes guild has been sitting on their laurels while freds guild has been actively assisting them.