Not necessarily, because as it's been stated before, 15% for someone who only makes $35,000 a year represents a good chunk of their spending power, while being an easily affordable burden for a large corporation. For small businesses, that 15% could be a new set of equipment, a couple new employees, or more incentives for those already there. There always needs to be an adjustment to account for all the different caveats that exist among all the different tax brackets.
It does, simply because low income folk have a much narrower subsistence margin than those who earn more. While there is something to be said about spending within your means, if the vast majority of your money is going towards rent, bills, groceries, and other basic necessities without any access to tax writeoffs for temporary relief, you have someone who is socially static. They're not growing the economy, and they have no means to climb the social ladder, since the majority of their funds are going towards treading water. You can offset this by offering up more social safety nets, or subsidizing education and healthcare to put their tax dollars to use for their own benefits. But you can't have an either/or situation, where someone pays taxes without the benefits that come along with them.
That $1B loss isn't so quite so bad when you still have $9B left after taxes. Anyone who makes that much is not disadvantaged in any way whatsoever. It won't make the difference between having a private jet or not, hiring more people, or giving more incentives for their current roster of employees because...
$10,000,000,000 isn't that much different than $9,000,000,000. No one making that much money will be operating down to the very wire. They could lose half of that (which I don't advocate) without suffering any real setbacks.