What are the benefits of having several state permits a practice that is generally banned throughout the United States?

This is when states become a “laboratories for Democracy”. This means that while federal law may say one thing about a certain issue/policy, there is sometimes overlap in jurisdiction that allow states to go against the Federal Government. A benefit of states being laboratories for Democracy is that they are able to implement policies that they feel is best for citizens of their respected state. A quality example of this would be the legality of marijuana. While marijuana is still illegal at the federal level, many states (colorado, california, washington, etc) have decided that the consumption of marijuana is legal for recreational use, despite federal law that prohibits it.