Because zero is not singular. In the context of English grammar, "plural" simply means "not singular."
Funnily enough even negative one is not singular. A debt of a single dollar is negative one dollars in your account.
Except...
> `1.0` books (?) – Martin Ba Commented May 22, 2024 at 13:3
:)
Funnily enough even negative one is not singular. A debt of a single dollar is negative one dollars in your account.