Hard to understand

I sometimes wonder, About when I'm dead and gone If any of my scribbles Would be read by anyone I am optimistic And take a positive point of view If "Happy Birthday" is remembered, There is hope for me and you. Simple nursery rhymes and sayings Have passed the test of time. Why are they remembered? They are simple, just like mine. I cannot understand how They have become so well-known, Did the writers have a system That was theirs to call their own? What sort of grapevine Or means of communication Did they possess Was divine information An answer to my quest? How did their scribbles Last through the ages Many simple words Adorn pages and pages. Of simple rhyme Why not yours and mine?