Dear OP,
IMHO, you should be looking at a very different question. Namely: why aren't I collecting the big money bonuses that are available such as the Chase INK 70K Ultimate Rewards points or the many others to be found on FT.
The bonuses are where the value is for most of us. Unless your spend is truly gigantic.
One RT in F to Europe or Asia is worth whole lot more to me than a few hundred bucks in cash back.