If the government fixes a price that is unprofitable to a supplier, then the supplier is less likely to sell apples, or any other product, to small retailers. The same is true for prescription drugs. Research and development on tomorrow's cures would decline. Certainly automobile, aerospace, and computer manufacturers, among others, make similar profits, but no one in Congress accuses them of price gouging for their vital products. Although it is true that some drug companies are financially successful, profits are spread very unevenly throughout the pharmaceutical industry.
Pharmaceutical research is a very risky business.
A number of independent studies have found that between 5,000 and 10,000 compounds are tried on average for every 1 that makes it into a neighborhood pharmacy. And that one may be for a very tiny niche market. The incentive to engage in such intense research and development is the potential for large profits on the few drugs that are successful. If the government limited profits on the successes, then there would be fewer resources devoted to research and development. This would translate into a reduced likelihood that tomorrow's cures will be developed.