I'm not a linguist, but in English it looks more "why are there only two versions of the verb" than "why we have the singular version of the verb". In French a

I'm not a linguist, but in English it looks more "why are there only two versions of the verb" than "why we have the singular version of the verb". In French and German (and probably other related languages), verbs have one form per "type" of pronoun. Too a lesser extent, English has that too for some verbs: I am, thou art, he/she is, we are, you are, they are. But the "I" case is often the same as the "he/she" one, and "thou" fell out of use, leaving only two forms.