Actually, this is not true. It's a well-known problem that "uncontacted tribes" actually suffer from continual outside influence, with people living near them actively trying to "civilize" them, or people with zero consideration for the law committing crimes on or near the lands occupied by the tribes, in some cases attacking and killing the tribespeople to accomplish their goals. For example "uncontacted" tribes in the Amazon have actually recently initiated contact with local government officials to ask for help with cartel enforcers that killed members of their tribes to make room for their grow / transport operations. And in another example, the "uncontacted" Sentinelese tribe in the North Sentinel Islands has actually been trading with local fishermen for years, but it was not widely known because contacting the tribe is against the law. It was only recently revealed to be the case after that stupid American missionary went on his quest to "teach the tribe about Jesus" ("civilize them") and was killed on the beach, and the police were investigating ways to retrieve his corpse.

We absolutely do not "leave them alone". Or at least -- in the grandest tradition of human hypocrisy -- we just all agree to say we leave them alone if anyone asks, and just sort of pretend like our laws are foolproof solutions to things like preventing interference with "uncontacted" tribes, or stopping drug addiction, or preventing gun violence, or what have you.

Uh, no. In the name of leaving them alone we don't bring disease and destruction to their culture and community.

Do you think we could interact with them in a beneficial way without bringing disease or drastically changing their way of life?

Ethics and moralities of actually doing so aside for two moments...

1) I'm trying to imagine a sterilized delivery system of treatments that such tribes would be able to understand enough to use.

2) Similar to "how do we communicate to the deep future not to enter nuclear waste storage facilities", how do we communicate to such people when not only is there a language barrier but also a gap of hundreds [thousands?] of technological &c progress as well.

Giving them gifts from the gods (i.e. packages without contact) would only make them reliant on us and could have unknown effects on their culture, increasing (if they have it) human sacrifice in times of illness, for example.

That seems a rather different situation : we are not a difference species, and this "no contact initiative from our part" policy include consideration on our own civilization defects.

That doesn't discard the interest of the point, but that brings a call for more specific nuances depending on civilization discrepancies.