[quote=@Meta]
<Snipped quote by Stabby>

Why should it matter who we tell?
[/quote]

Because existence is dangerous and it could be harmful to either themselves or others should they or dangerous entities within their world recklessly seek to gain access to it. Existence has enought problems as is, introducing new entities, parties, and possible threats to it is just making things worse, especially if these worlds are unable to defend themselves within existence once they access it.