Hoping is the present participle of hope. Moppinghopping is the present participle of mophop. Hoping has only one p while moppinghopping has two. What difference does it make? Why is hoping not hopping?
Edit: I changed mop to hop because of a comment by Kat.
Kat: Why would you compare hope to mop instead of hope to hop (in which case I think your answer will become obvious)?