On the Imperial side you fight for two towns. Whiterun (which I believe also happens when you play the quest for the other side) and Windhelm in which you finish up the fight inside the Palace of the Kings (definitely, therefore, inside the actual town).
Yes, they put a little effort into two places. But the Riften, Dawnstar, and Winterhold work is pathetic. Can't say that even the two city attacks are all that interesting, since it seems like barely anyone is in these "armies." The whole Civil War questline is extremely shallow in terms of depth of play. Like a lot of things in TES games, really.
It makes sense that you don't fight for the other towns. Falkreath's people support Ulfric, the former Jarl supports Ulfric, only the corrupt puppet Siddgeir supports the Empire. Same for Winterhold, although that place is not worth the men to battle for it. And so on.
That just isn't true. The people, if they comment about support at all, are all over the place in all cities. And it isn't like they comment on how they even get control of those cities. They just suddenly come under control after you take a fort and talk to your leader. There's no talk about whether there was a war, siege, or what, because apparently even the effort to explain what is going on and how that aspect works wasn't deemed worth the time.