Unicode is vast. There's absolutely no good reason we don't have Snowman Separated Values (or some other proper separator sign that isn't commonly used elsewhere) other than that people don't demand it.
Where can I find those on my keyboard? Entering escape sequences by hand isn't user friendly, if it works at all. One of the benefits of csv is that it's universal, I can open it in vim or write an awk script to extract values, someone else can open in notepad++, someone else should be able to open in excel.
Just thinking out loud here, but isn't part of the point is that they are not keyboard characters. If they're on the keyboard, then they will pop up in ordinary text, similar to the | (pipe) character and friends.
They are ^\ ^] ^^ and ^_, respectively. Of course, most text editors will interpret those keys as something else. In emacs you can enter them literally by using C-q (quote) first.
