I think what stops many people from starting wars is that the fact if they lose they lose everything.
Losing evenly matched wars are perfectly fine to me but fighting a gigantic empire with one city realm doesn't sound fun at all and this game has turned into just that. Big realms crushing smaller realms.
similar to what someone else said though that's not entirely true, it's also been said big realms are less fun to be in during war because there is no edge, worry, or feeling like you need to act.
