Some people referred to prohibition as a ""noble experiment"" because it

forced people to improve their morals.

Explanation:

The prohibition prevent people from consuming alcohol, which is dangerous for their health and overall well-being so it is automatically improving the morals of the people by forcing people not to consume alcohol. This question refers to the law that 'prohibited' people from consuming alcohol, since it is not an awareness campaign but a law that tried to improve the morals of the people so it is a Noble experiment.