The obvious answer there would be that you get wiped out if you’re too loud, hence the only surviving civilizations are the quiet ones. We wouldn’t’ve been met by a friendly transmission politely informing us, but rather whatever the cause for this silence is - some force so overwhelming that it possibly inadvertently wipes out nascent species.
Say, for instance self-replicating artificial space probes designed to seek out “new life and civilizations” gone wrong. So, deep space is full of these things and if a star draws their attention, all of them within transmission distance make a beeline - say hi and then proceeds to “salvage” any usable matter in the star system to replicate themselves and spread out again, thereby also dooming whatever life attracted them in the first place.