Here's why:
* Subject-verb agreement: The verb should agree with the subject. "Him" is an object pronoun, not a subject. You would say "He and you" or "You and he" as the subjects of a sentence.
* Pronoun order: In formal writing, it's generally considered more polite to put "you" before "him" in a compound subject.
Examples:
* Incorrect: Him and you should go to the store.
* Correct: He and you should go to the store.
* Correct: You and he should go to the store.
Exception:
There are some informal situations where "him and you" might be acceptable, such as when using it as a shortened form of a phrase like "between him and you."
For instance:
* "Between him and you, I think the party was a flop."
However, in most cases, it's best to stick with the standard grammar rules.