Yeah, the big issue is that any code that took addresses from user input had to do validation to make sure addresses were valid, in allowed ranges, etc. While

Yeah, the big issue is that any code that took addresses from user input had to do validation to make sure addresses were valid, in allowed ranges, etc. While the sockaddr struct allowed to to abstractly handle v4/v6 socket connections, there wasn’t a clean way to do all of that additional stuff and IP address logic leaked into all kinds of software where you wouldn’t first expect it. Something as simple as a web app that needs to inspect proxy headers would even have it. It also didn’t help that it became practice to explicitly not trust the addr resolution offered by the sockets API because it would do unexpected things like resolving something that looked like an integer to a uint32 and then a 4 byte V4 addr.