The whole reason why there are so many members (and very active ones at that) is precisely because sig campaigns and bounties exist. If they were banned right now, I'm sure there would be a mass exodus and there wouldn't be nearly as much "discussion" going on. Bitcointalk would still probably be more active than any altcoin forum, but compared to how it's been since the first sig campaign it'd look like a ghost town.
Also, OP made an excellent suggestion about reading very old threads. Some of the ones from 2009-2011 are fantastic, and I'm sure there's a lot of good stuff from the pre-sig campaign era for anyone who wants to learn a bit of bitcoin history.