Like you said happiness is an electrochemical state. A state of a biological computer purpose built with the obvious intention to survive and reproduce.
Suppose you are the architect of the universe, why would you create such a creature? Natural selection must be beautiful, or necessary for something beautiful and worthy by your arbitrary fancy.
If we could exist as spirits then there would be no need for a body or a brain, no need for fear, and thus no need to be separate from each other. In other words even given the premise that god wants pets (or children even though he supposedly invented the concept of children from nothing so it's not like he would have a pre-existing itch), the angels should have been good enough.