He is special, she is special, they are special, we are special. In each of these cases, singular he/she takes verb associated with singular entity and plural we/they takes plural verb. By this analogy, there should have been “You is special.” However, “You” as personal pronoun despite denoting a singular entity takes the plural verb in present infinitive form. I wonder if this grammatical feature evolved as part of giving respect to someone on the other side while interacting face-to-face. Maybe, the tradition of “You are …” when used as personal pronoun started when society became over conscious of giving elders/seniors due respect (plural meaning more and so more respect in this context).
Would like to seek others’ opinion regarding the above.