I doubt the decision is just up to Hertz. In any of these partnership deals (for example, Centurion Platinum status on Delta), there is some type of give/take negotiation with American Express and the other provider. What seems likely to me in recent erosion of benefits (for example, SPG/Marriott status, or the GoGo passes for Business Centurion), it became too "expensive" for American Express to continue offering that level of status on the contract renewal. Thus, they have conceded the issue and tried to substitute other things for the card member. I think most of us agree this has been a (significant) net loss of value because the substituted items aren't very worthwhile.

I think the "gotcha" American Express has over this whole Centurion program is that the members driving the highest spend find the points valuable enough that they keep the relationship going even though the card benefits just aren't there any longer.