It matters because Mitt & his peers have no real use for more money, other than to exercise more power over the lives of the rest of us, and because there is no infinite pie. Sure, the total economy might grow, but that doesn't matter if they get all the growth & more, does it?
How about trying to collect taxes from people whose meager incomes fuel the economy with every dime they get, whose spending is the backbone of commerce in general? Why? to satisfy some perverted sense of superiority on your part? So that Mitt can have more?
Why do you think he's entitled to more, anyway?
This is generally my thought on the subject. While I certainly understand that big money can result in big business, the reality is that big business people are interested in generating more revenue. Part of that is laying off work force. So, they get tax breaks because they can greatly benefit others by creating jobs, but ultimately, if firing Jan saves them $30k/year, they'll do it to create bigger profits.
That's not to say that it is wrong, but the reality is, many job creators ultimate interest is lining their pockets, or their share-holders pockets. If laying off 30,000 people is acceptable for a short term to increase profits, they'll do it.
So ultimately, the only way to ensure that many people have jobs is to provide incentives that are directly tied to just that, creating jobs. For every job you create, you get X dollars off of your taxes. For every job you remove, you get X dollars added back to your taxes. Basically cutting some incentive to perform mass lay-offs, which may or may not sway the decision in a different direction.
Ultimately, this country allows many people the opportunity to succeed as they do. If I am capable of earning a 6 figure income year after year, I should pay a little more than the guy who can't. And the higher you get on the scale, the less the difference matters. You take $5000 away from someone who earns $25k, and you've just put him below the poverty level, and getting by is going to be extremely difficult. You take 50k away from someone who earns 200k, and now he won't buy that Escalade he had his eyes on.
Ultimately, both affect the economy, as that Escalade puts some people to work. But the reality is, that guy will just buy a 35k-40k vehicle that is a bit more reasonable for him, which still puts people to work.
I suppose I can be completely in the wrong here, but to me, if I am fortunate enough to earn a high income, I believe that can be attributed to the opportunities this country allows. My success, while largely due to my own efforts, may not be possible in some other countries. My share of taxes should be equal to or greater than those that haven't had that level of success.
And of course, that opinion could change if I ever get to a higher level of earning. But at that point, I'll have a much easier time meeting all of my expenses.