Any kind of application that acts as a server needs a direct IP connection.
Gamers get errors about "strict NAT." Traditionally the solution to this problem caused by NAT was to forward the ports. If their ISPs has chosen CGNAT port forwarding is impossible.
VoIP calls that have one way audio are a symptom of reachability issues caused by a firewall or address translation problems. VoIP services have adapted to IPv4 NAT by relying on proxying instead of STUN but CGNAT really degrades reliability.
Video chat uses the kludges of TURN when peer to peer connectivity does not work. This increases costs for the video chat service who in turn require a paid subscription as they will not relay traffic for free.
BitTorrent and file transfer services need direct IP connectivity. If p2p file transfers worked on any network we would not need to mind Gmail's 25MB attachment limit, or pay for intermediary cloud storage.
IPv6 has marginally lower latency (in most cases) and lets peer-to-peer applications work flawlessly. If your ISP only has v4 CG-NAT then it gets you a lot better connectivity.
Their devices continue to work when a scarce resource is no longer plentiful. The every day user doesn't need to care, but the people working on the stuff the every day user has need to care.
