To me, this is offering one's customers much greater value than just some points that can be redeemed only with that company.

This is counter-intuitive under the system we have. A company does not usually want to create a reward program which benefits another outfit. Welcome to cryptoeconomics. This changes things considerably.

A company that is doing this here offsets the "loss" by that reward being used elsewhere if it holds STEEM. Since this adds value to the ecosystem as a whole, the fact that my reward tokens are used elsewhere in the ecosystem still benefits me.

It's really simpler than that. A reward is a reward. Its purpose is to benefit the rewardee. It would not dish out the rewards to anyone. It would've benefited before giving the rewards.