What if the girlfriend is serious, but maybe not as serious about the relationship as OP? She should accept a gift that is above the relationship rank, because of "generosity"?

There are a lot of reasons why someone might be less-than-delighted with that gift.

What if she is part of an endowment that pays for such matters, and it isn't a problem for her-- making his gift totally stupid and superfluous?

What if she is actually very nervous about driving, and isn't ready to admit that she is not quite ready to spring for the license?

It's a damn expensive gift, I'd be hesitant about accepting it-- we don't know their relationship-- maybe she thinks if she accepts it she will have to drive the OP around!