Let me see if I can make an argument for why they're actually good. First, especially for the SoCal, Bay Area, Oregon, and Arizona schools, it's pretty feasible to take in both games in a weekend, and so they make for a nice "home and away" series as with other sports (like Soccer) that do that.
Second, what I like most about it is that I'm often not as familiar with, in my case, Cal in any given year, but watching them play in the first game gives me lots of thoughts about how they could better adjust to Stanford, and vice versa, how Stanford could adjust to their specific players, style of defense, sets they run on offense, etc. From a tactical standpoint, it's really fun to see how both teams adjust in just two days, because there are unlikely to be personnel changes or player growth in that short of time, so it's all about rapid fire adjustments.
Third, as others have said, it's much harder to beat the same team twice back to back, which tends to make the second game more competitive than I think it otherwise would be.
As strange as it sounds, I now actually look forward to the home and away civil war weekends, even in the years (like this one) when the paired team is really not very good.