I forgot to mention that C-strings also handle human readable data input and output, so they are the primary basis for human-computer interaction.
You still read text and numbers on a screen and type in names and numbers on a traditional or touch screen keyboard, so no, it is not an "old tradition that survived". In fact text is an essential means of data transmission that is extremely difficult to replace.
As you know, since you want to transmit a human readable message.