I'm not happy when they raise the redemption rate either, but it really is no different than when a store or restaurant or hotel raises their price for something they sell. To be honest, I don't understand why people don't understand that this is to be expected and why they get so upset when it happens.
This program is a giveaway. Yes, you spend time, but the rewards are so small compared to the time you spend that you would not do it unless you had spare time to burn. It is not as if you could calculate that you are being rewarded for your time, because if you really looked at it that way, you surely would never do it.