The Beatles experimented with drugs, they took stuff that kept them awake in Germany and Dylan turned them onto Marijuana but I think LSD had the biggest effect on their art particularly for John but only for a short period Sgt Pepper/ Magical Mystery Tour. I think LSD may have helped George start his spirituality, seeing things in a different way, he moved on but I think he incorporated what he got from LSD into his world view. John and Yoko i think did Heroin for a while which strikes me as a really awful drug, not mind expanding or artistically enriching but highly habit forming and personally degrading.
Funnily Paul did the famous interview where he admitted taking LSD but he was the last to do it and I don't think it changed him or his music much. He liked Marijuana, I suspect never got into harder stuff (except alcohol for a bit after being put out by the breakup of there Beatles)
As you say though they left there fans to decide and we could benefit from their explorations without having to indulge ourselves.