Other, primary reason: Complete, unabashed escapism and wish fulfillment. Secondary reason: because it sure beats lying comatose on a mattress for eight hours a day. Tertiary reason: to hopefully learn time distortion and give myself the ability to live out subjective days, weeks, months, whatever I can get during my dreams. Coupled with wish fulfillment, I'd like to see if I have the mental brawn to invent consistent fantasy worlds and actually live new lives inside of them.

Note that I'm not saying I want to sleep all the time to experience these things, only my physiologically allotted 7-8 hours a night, which is why time distortion is so big, and why I hope it's as true as some people claim.