With IPv4 scarcity, many carriers had to employ NAT (network address translation) so that many users are mapped behind a single IP at the same time. This of course makes impossible to put a personal server on a local home network because although connecting to external addresses is still doable, any incoming packet wouldn't know which one of the users it should reach without explicit rules that the users have no access to.
It also means you will frequently be blocked by services such as cloudflare if anyone else you're sharing an IP address with is infected with a spammy virus.
I’ve been behind CGNAT once. It was a miserable experience for this reason. (No idea how many people there were at the one IP address, but https://iknowwhatyoudownload.com/ reported on average ten or twenty hours of video per day being downloaded via BitTorrent from the address, none of which was from my endpoint.)
