It's the fact that the span of time of the world moves forward, yet the technology/setting stays very similar. It makes the setting become bland over time if it's just the same thing done over and over. Imagine 15 years from now and 5'ish TES games down teh road if the world was very similr to Oblivion technology wise, it wouldn't get a bit stale to you?
No it wouldn't. We love TES for what it is, if you don't; Too bad.