There’s a selection bias there. Only the most xenophobic and violent uncontacted tribes would remain uncontacted.
(they could either maintain a subculture, or fully integrate and become indistinguishable. either way, they don't necessarily die off when they make contact)
Not sure what word is a better choice though. Maybe someone can reply with one.
i don't really have any idea what the ratio is. i do know that there are a ton of traceable groups from ancient times today. i don't know that there isn't an even larger number of groups that didn't make it