I don’t use drugs nor alcohol, but I just turned 18 and I noticed that a lot of people younger than me (high school age so 14-17 even) use alcohol and sometimes drugs from siblings, older friends, etc.
Did you do that when you were younger than me? I don’t plan on doing so anyway.
There’s an Alcoholics Anonymous meeting in my area called “Never Had A Legal Drink.” It was created by and for people who decided that they were alcoholics and had to stop drinking before they turned 21.
Plenty of people get into drugs/alcohol at an early age.