I'm aware that the term loophole is prejorative, but they are the carrot working with the stick (higher tax rates). We (progressives) certainly like to point out that tax rates were significantly higher in the past (90%+ under Ike) but ignore the reality that virtually no one actually paid that rate.
True progressive taxation allows businesses to grow and flourish because the money that is reinvested in labor and expansion would have otherwise been "lost" to taxes. The owners/shareholders can look at $1 billion in gross profits and choose between paying $900 million in taxes or reinvesting that money in payroll, (with generous tax credits for doing so). Get the balance right and the owner/shareholders get more of their $1 billion to keep, increase payroll (capacity), and probably still pay a fair share of federal taxes.
Follow the GOP model and there is no incentive for hiring anyone or improving factories and the uber-rich simply pocket the excess profit. It is a short term gain for them, but "short term" is relative and it will be their decendants that end up owning broken, under-funded businesses. That is one of the problems in the US right now - our tax code actually favors taking money out of a business over investing in that business.
In a sense, if the rates and policies were more progressive, some capital expenditures would and probably should result in lower effective tax rates. I don't want the billionaire's money, I just want that money to be used effectively. If it were, there'd be plenty for me and more than enough to maintain strong social programs.