IPv6 doesn't solve the Airdrop problem. It'll only work at reasonably-fast speeds in the rare case that both people are connected to the same wifi network - but there's already tools like LocalSend[0] for that. Having a file go via cellular provider A, halfway across the country, through some IX, halfway across the country back, and via cellular provider B tends to make things a bit slow.

Similarly, using P2P for game VOIP is a Really Bad Idea as it basically doxxes the player. Even 1v1 lobbies aren't always with people you trust enough to invite them into your house, so you shouldn't be handing them your IP address! In 99% of cases it is better to proxy it via a server instead.

[0]: https://localsend.org/