Even a decade ago, you would have needed to support Unicode if you handled any of those strings. IDN domain names existed as far back as 2003, so unless you cou

Even a decade ago, you would have needed to support Unicode if you handled any of those strings. IDN domain names existed as far back as 2003, so unless you could guarantee that everything was in A-label form already, you would need to worry about that (which affects URLs and email addresses as well). URL paths might be Unicode if no one normalized it to percent-encoding first. And HTTP headers--like email headers--could well be non-ASCII despite the standard prohibiting unencoded non-ASCII text because the real world is full of shitty implementations that don't follow standards, and the internet community generally runs on the principle that it's better to force everybody else to try to make sense of the result than tell those people to fix their code.