Being 20 I'm sure you have tons of experience. Have you ever met a person who has done crack or meth? They have no control and can not use the drug for recreation. It eats their teeth and body turning them into a bag of bones with no teeth.
Or pcp. When I worked at a jail the same 18 year old kid would come in every few weeks high on pcp. I Would talk to him and try to understand why he liked getting so high on the stuff. He would come in paranoid thinking everybody was trying to kill him and have to be placed in the padded cell. One day he came in high but after the time it usually took for him to return to normal he never came around. He had permanent brain damage and didn't do much more than drool from them on.
I know another case just like that where a mid twenty guy did so much pcp he is in the same shape. He is now on psyh meds and sets in a chair in front of the tv drooling. He is now dependent on his family for everything. Also on occasion he wonders off and the police have to be called to find him.
Or maybe a more personal story of a extended family member that is 17. She smoked one of the fake weed products and had two brain aneurisms. After a few weeks on life support she started breathing on her own but is still blind with hardly any motor function. She can not talk and will never be the same again.
How about these bath salts that are making people hallucinate and eat people. I wonder if the people who were killed and eaten would agree with you?
By the way. We do not put people away for ingesting things. We put them away for possessing things. The charge in possession of a controlled substance, not ingesting. If you have already ingested the dope and have no more you might be arrested for public intoxication or DWI if your driving but not PCS.