Edit: For clarification, if it's the type of rebate typical in the US, that means I get it later and I can't afford the fuel now. If it's a rebate that's done at the time of purchase, then it wouldn't seem to make much difference, on average.
Let's say it's annual (or if they have the capacity, monthly) and paid at the start of the passage of the law, so you get the money first before the gas price increase.
It's not done at time of purchase because it is not a gas subsidy.
Edit: For clarification, if it's the type of rebate typical in the US, that means I get it later and I can't afford the fuel now. If it's a rebate that's done at the time of purchase, then it wouldn't seem to make much difference, on average.