You don't know it isn't fun. You haven't given it a chance.
Let me give you some examples:
I played the Deus Ex demo and didn't really find it interesting. A short while later I got bored and saw a copy of DX on the shelf at a local game store and thought "What the hell, I've got time to kill". Installed it, played it, and by the time I was done it became one of the greatest games I've ever played.
Same with the Arkham Asylum demo. I didn't really like it that much. 2 years later I play the full game and it turns out to be one of the best games I've ever played.
I didn't like Halo:CE the first time I played it. Then I got Xbox Live, and Dave bought Halo 2. So I bought it so I could play online with him, and that's how I met Andrew and Logan! I loved it, went back and bought Halo CE, etc...
Point is, you can't judge a product after a 30 minute trial. You have to dig a little deeper than that.