Because they dodged and hid their money offshore and on (remember Enron and Worldcom's fancy bookkeeping?), and then Bush repealed those tax increases and allowed even more tax havens.
The capital gains tax is, frankly, far too low, and loopholed to the max. It should be calculated from unadjusted revenue minus unadjusted gross expenses for real goods and services, and those goods and services transactions audited as far down the dollar chain as it's possible to go, so that false or shady transactions can't reduce the tax burden. And that's the rate. It can be a low rate or a flat rate or a progressive rate or whatever rate you want, but it should apply evenly across all corporations and people without exceptions. Should even apply to churches, nonprofits and charities. No exceptions to the capital gains tax. Then we'd have a system that isn't gamed and subjective.
And then, of course, address seriously all the disparities and lopsided shit like drones and stealth bombers that we buy with all that tax money, because if we had a fair tax system, we should have a non-insane spending system too.
And while I'm at it, My Little Ponies for all the children, beer for the dads and girls' night out for the mommies. And unicorns and rainbows coming out of my butt, with a pink cupcake and Greek Gods serving us free Starbucks from little push-carts that roam the neighborhood, and stacks of money thrown on our doorsteps by conga lines of happy Oompa Loompas who don't feel oppressed.
Or revolution and just take back what the 1% stole from us and frog march them to the guillotine...
I'm good either way.