What's wrong with giving the tax credit to the leasing company? That just allows them to price it lower. (Similarly, it ideally doesn't make a difference whether you apply sales tax to consumers or sellers. The equilibrium will adjust so that the net money paid/acquired by each will be the same.)
1) It shows consumers that their gov't is supporting this. That's good for citizens to be aware of, regardless of whether you think this credit is a good or bad thing.
2) Ideally, it shouldn't matter but I don't trust car salesman to give consumers the best part of any deal. Consumers are generally not equal negotiators and I suspect sales people will pocket more of the tax incentive.
They can say the car is discounted to include the incentive but they may not apply the entire incentive to the discount. The more complicated a deal is, the less likely a consumer is going to get the better end of that deal.
That may be fine if you're favoring a completely free market but I prefer to side with consumers and favor protection when possible.
