Language & WorldMental model
English didn't lose its formal "you", it lost its informal one.
Linguists call the choice between familiar and polite pronouns the T–V distinction, after Latin tu and vos; the term comes from Brown and Gilman, 1960. It began in the 4th century when Roman emperors were addressed in the plural, a metaphor for power. German du/Sie, French tu/vous, Spanish tú/usted have it. English had thou and you; the familiar thou disappeared.
Useful: When you address everyone as "you" in English, strictly speaking you're being formal with all of them.
Source: en.wikipedia.org