The main reason people do drugs is just to have a good time.
Alcohol - makes you more social at parties
Marijuana - makes you calmer/relieve stress. Also makes everything hilarious.
Shrooms - makes you want to go on adventures
Salvia - trip balls for about 5 minutes
Drugs and alcohol simply make experiences better for the most part when used moderately. Used to much and you run the risk of addiction and serious health issues in the future.