Probably because the greedy corps are paying more than anyone else.
Why don't the greedy corps pay the locals even more?
If they wanted to, they couldn't, because it would destroy the local economy. Perveyors of goods would raise prices to take advantage of those working for the greedy corps, and anyone who couldn't get a job at a greedy corp would have to go without food and clothing. These economies have to be brought up in stages, and as equally as possible. Greedy corps paying a bit above local wage will help, if there are enough of them.
Why buy a yacht? Well, because you would enjoy one. As a side effect, it happens to employ a large number of people who build, sell and maintain yachts, who might otherwise go hungry. Checked what it costs to maintain a yacht lately? All that money is going to people who need jobs. Same for sports teams. Sometimes the most "worthless" activities are the ones most efficient at injecting money into the local economy.
Now, you are right that controls have to be placed, and execs of megacorps are currently spectacularly overpaid, and people should pay attention to who they are electing. The disparity of earnings will eventually make the U.S. into a 3rd world country if not controlled. Third world countries always have a few spectacularly rich people and everyone else poor.
Don't vote for Democrats or Republicans? Well, you have to be careful there too. Remember, it was Florida Nader voters who elected President Dubya.
Basically, if you have money, spend it. Others need the jobs. If you have a lot of money, spend a lot of money, even if it means buying a bigger yacht - keep enough to secure your own future so you won't become a burden on others late in life. Sometimes the greedy megacorp is providing the best value and deserves the business, sometimes not - but at this point in our economic / population cycle, buying just what you need is likely to result in economic collapse.
Probably your job (or next job if you haven't gotten one yet) depends on people buying things they don't need.