Why hasn't my book made any money?

i have published fore poetry books and have made no money at all, the way i right poetry is a very simple way i could teach it to any body and they could wright an unlimited amount of publish quality poems but if i tell everybody it would most likely destroy the poetry world because there would be a overdose of publish quality poems , do i right a forum on the way i wright poetry thus making everybody that reads it the ability to wright perfect poetry and watch the poetry world destroy it self or will somebody tell me why i can't make any money on these four books?