If nothing else, psychotropic drugs serve as a great reminder that the way we perceive reality is simply the way we perceive it. When a chemical can change so drastically the way which we experience the world, that is proof that our version of reality is one version among many possibilities (none of which I'm arguing are "right" or "wrong"). We hear sounds in a very distinct bandwidth. We see light in a very distinct bandwidth. We taste and smell only that which we can taste and smell. And it is all mixed together in a specific way that allows us to discern what is important and what isn't. There's a lot more going on in the universe than any of us can ever know. It's difficult to understand this (in a visceral way, even if we recognize it intellectually) until you've experience the world in an altered state of mind. For that reason, I think many more people should try LSD or mushrooms, or whatever else might do it (never tried MDMA, but seems like that has some similar effects).