***** NOT A TEACHER *****
What a fascinating question, Shatiloff.
I shall keep my opinions to myself, but I felt that you would be interested in the following information that comes from a great grammarian.
1. "The Midland [area of England] developed in the fifteenth century a peculiarity of its own -- the suppression of the end of the third person singular indicative."
2. " 'John Dam kno' ... instead of knows."
3, "Shakespeare has observed this peculiarity of dialect. ... 'The town is beseech'd, and the trumpet call (for calls) us to the breach.' "
4. "Traces of the east Midland peculiarity are found in our early American documents written by people from this part of England."
5. "It is still found also in American dialect." [Only my note: You will have noticed that some American singers continue to suppress the "s." For example: "She love me."]
-- Source: George Oliver Curme, A Grammar of the English Language, Volume I (copyright 1935), page 246.