It appears that the current form of English only has the casual or irreverent form of pronouns like "you" and "I"; English lacks the formal or respectful version, which is present in many other languages. By contrast, in formal Hindi conversations, one refers to the first person as "hum" which roughly translates to the regal "we" in English. One refers to the second person as "aap", which translates to "thou" in archaic English, but appears to have no equivalent in current English.
In which historical era did English shed the respectful forms of pronouns? What was the historical context of such linguistic pruning?