This is a simple question, but I can’t figure it out.

I have a basic button in SwiftUI:
Button("Sign out") {...}
This works fine ans shows a button with “Sign out” text.

I want to extract my texts to a separate file doing it like this:

struct ProfileViewLabels {
    static let SignInButtonText = "Sign in"
    static let SignOutButtonText: String = "Sign out"
}

Using it looks like this:
Button(ProfileViewLabels.SignOutText) {...}

This causes an error:
Cannot convert value of type 'String' to expected argument type 'LocalizedStringKey'

The button is defined like this:

public struct KlikButtonOutline: View {
    let title: LocalizedStringKey
    let disabled: Bool
    let action: () -> Void
}

I do realice the the input is declared a localizable string, but why it "Some text" a localizable string and let text = "Some text" not?