I like the fact that as Romans you have to keep an eye on things like this - it makes for more unpredictable campaigns, which in turn leads to more replayability. There's also the converse side of rebelling, which is having rebel generals and their armies join you out of the blue. Sometimes you can end up with more gold shielded peasants than you can shake a stick at, but more often than not you get some decent troops and a new general or two for free. Bargain!