This is only if you want strings to be sequences of bytes. If you want strings to be sequences of code points, it is more sensible to define string length as the length of the sequence. I prefer the latter (for coded text) because it is closer to the meaning of the string. Sequence of code points is always sequence of code points, but a sequence of bytes may not correctly encode a sequence of code points, and bytes in encoding are not in one-to-one correspondence with code points in string. So I see no reason to care about individual bytes per se in the string's code.