Why `Value` is `pub` while its bound `Sealed` is sealed?

[tisonkun]

pub trait Value: crate::sealed::Sealed {
    /// Visits this value with the given `Visitor`.
    fn record(&self, key: &Field, visitor: &mut dyn Visit);
}

mod sealed {
    pub trait Sealed {}
}

I don't see a solution to implement Value in application code. I can see that it is possible using DebugValue or other out-of-the-box implementation for boxing the value, but why Value is pub while its bound Sealed is sealed?