In the case of why transfer essay in addition to why us, I would say something along the lines of what lindagaf suggested in #9. Just try to keep it positive, and that you are focused on finding a better fit for you.
Academic reasons should be primary as compared to non-academic reasons, and they should get more play in the essay. Examples include seeking a major that the current school doesn’t have, or you desire a more collaborative environment/smaller classes/greater prof accessibility/specific research with X prof/specific classes, etc. Then you can mention the non-academic things…more school spirit, etc.