Because the products that are produced today require a very structured division of labor. Sureley, workers who pick crops in Central America can not be paid well and at the same time those in North America afford to buy those crops:

Why would any employer pay those workers more than a few cents/dollars a day, when there are people willing to work for those few dollars/cents out of necessity? The employer can pay less to the worker, thereby charge consumers less for the product, thereby take over most of the market for the product, and thereby force others to pay their workers less.

Show me a scenario where those doing jobs that require the least capital, such as crop pickers, are paid a decent wage? I don't think it's possible under a capitalist system.