If consenting adults partner together to commit a crime why aren't they equally guilty of it? Why aren't they punished equally for it?

Depends on the crime, depends on the actions of the perpetrators....You're nor cloning this question from the drug dealer question are you ? 

They usually are.

A getaway driver won't be given the same charges as the one who went in the bank and brandished a gun.  The vagueness of your question makes it impossible to answer accurately. 

not sure why but they should be