You yourself point out the reason to have a tax at all: because someone has to pay for the cost of the US government. Also, at least in the versions I heard about this was a very carrot-and-stick tax bill. It didn't just allow companies like Apple to repatriate their foreign cash hoards at a lower tax rate, it taxed that foreign cash at the same one-off rate whether they repatriated it or not. The whole point was to remove all incentives to not repatriate money, to make it futile to try and wait for some hypothetical opportunity to do so at an even more reduced tax rate.