At first there was no plain text. Then ASCII became standard enough and if you passed a file to someone they would be able to read it without you needing to te

At first there was no plain text. Then ASCII became standard enough and if you passed a file to someone they would be able to read it without you needing to tell them an encoding. Extensions of ASCII and other options spread, and there was no way to have plain text include characters beyond the 128 of ASCII. Over the past decade or so we've been consensing on utf8, however, and the probability that some random piece of non-ASCII text is utf8 has been getting sufficiently high. There is plain text, and it is utf8.