Hello SpiritImage and welcome
Although your question might have been directed at Steve I'd like to add a few thoughts.
If you need anyone to convince you as to why you should do something then perhaps that something isn't for you.
If you are interested in astral projection... I've been recommended a book- Adventures Beyond the Body: How to Experience Out-of-Body Travel by William Buhlman.
http://www.amazon.com/Adventures-Beyond-Body-Out-Body/dp/0062513710 The best means of discussion on a topic where not much is known is to engage personally and gather your own experience. Then we can relate and try to form a better understanding of what astral projection really is.
From my research, I have read we all leave our bodies when we sleep but lose consciousness just before and begin to dream.
I think when it comes to astral projection, they key word is projection. What is gained by this exercise? I disagree with your research that concludes we "leave our bodies" when we sleep. Where, then, do you presume we go, and what is that entity that goes? That is the thing to find out.