Because its a stupid move to assume that if you liked something before it will be equally good again.
With the rising prices that they charge for games these days it seems utterly daft to me to want something based on a two minute trailer
I think people want everything from games these days. The game will be around £30-40 on release (depending on vendor) and you will get a minimum of around 20 hours on a game like this. Of course, if you really enjoy the game, you could go into the 1000+ hour range on MP, etc.
If you find it's not for you, then you go to the pub and have a few pints 1 less times that month. Not the end of the world.
BO4 was the first COD I bought since MW3 and I enjoyed it - probably had around 100 hours played total. Was it the best game ever - no. But for something that cost me £30-40 at launch, it was a good investment.
They are releasing the game with a new engine (the current engine has been the same since COD4?) and no season pass. The trailer looks great and at this stage is definitely worth the punt.