An important rule in English grammar is "subject-verb agreement". It basically states that a verb must conform to the form of the noun (i.e. Singular/Plural). My question is:
What is the purpose of this rule?
It doesn't seem to play a huge role in semantics at all. "He drinks coffee" and "He drink coffee" both make sense and the -s at the end doesn't seem to add to the meaning of the sentence at all