Answer:
The desire to alter one's consciousness is a perfectly natural, normal one. It starts at a very young age: when we're kids, we run around in circles and make ourselves dizzy, just to enjoy the head rush. Or we lean all the way back while on the swings, so the earth and sky seem to spin around. As we get older, we find other ways to alter our consciousness: some people enjoy the adrenaline rush of extreme sports like skydiving, or the post-exercise "high" you get after a good workout. Others like to drink alcohol, or smoke marijuana, or take other drugs.
The high you get from hallucinogenics can be a very profound thing. I know that sounds all hippie-drippy, but that's just the way I feel. Mushrooms don't literally make you hallucinate -- meaning, you don't start seeing stuff that isn't there, or not seeing stuff that is there (unless you eat a whole, whole lot of them). Rather, everything seems to move and shift and stretch and ripple and pulse. For example, a dirt road might look like a moving river of dirt, or all the flowers on a bush might look like they're rotating in circles. It's more than a high, it's an experience that you never forget. Unless, of course, you have a lot of bad, unhappy thoughts at the forefront of your mind, in which case it will just make you dwell on all those bad thoughts, and magnify them in your mind, and you'll be miserable.