In practice you often do because it's common to parse text that has "special" characters which are always ASCII. Think CSV, XML, JSON, source code, that sort of

In practice you often do because it's common to parse text that has "special" characters which are always ASCII. Think CSV, XML, JSON, source code, that sort of thing. These formats may have non-ASCII characters in them in places, but it's still a very common task to work with indexes into the string and the "character" at that index, which works fine because in practice that character is known to always be a single code unit.