This does not appear to be necessarily true: a provision could be negotiated whereby the poorest continue to receive a tax credit.
P.S. It is damaging for credibility when you claim that people are rewarded for not paying a tax: they are not rewarded but assisted, and not because of the nonpayment of tax but because of relative poverty.
You miss the whole point. This would perpetuate the existing system, where people vote for whoever is going to give them the best deal.
The idea is to exempt certain items, like food and medicine, not certain income levels. If you exempt certain necessities then it puts everyone on an equal footing from the start. This would make it almost impossible to buy influence with the voters. This is another reason why it's not gonna happen in our lifetime.