Why does the government grant patents to companies that research new drugs?

The government grants patent monopolies as an incentive for companies to continue researching drugs. These patents last for 20 years and are supposed to protect drug companies from other companies who produce comparable generic drugs. If there weren't patents in place, the companies would lose out on money because of the money spent in research and development. Companies who produce generic brands can sell their product cheaper without having to worry about spending money on R&D. This is why patents are granted, thus, giving companies to ability to price their drug at whatever price they please. When they are priced high, they claim that is for the money spent on R&D, but their financial statements show that they spend more money on marketing the drug than actually researching and developing it! That says a lot!