Very true. Sieges also stopped being special to me rather early on, as I was able to participate in the siege of several castles and towns only shortly after having joined the kingdom. When I joined the first siege, I was naturally very excited, but then I was already experiencing my second, third, and fourth sieges shortly after the first one. I believe that a siege should usually feel like the siege, just like a battle should feel like the battle, but they just seemed to happen so often that they became less special to me. A hostile kingdom was already snowballing in my game at that point, so it could be that the other kingdoms also got aggressive as a result, but we were taking, and losing, castles left and right. It likely also goes back to the thing about kingdoms having multiple armies running around at the same time, which allows them to conduct more sieges. I personally would prefer larger, more memorable sieges over the smaller, more frequent sieges that we seem to have now.
Let me know if you didn't have the same experience though.