Those would be Pascal Strings (length at the start, then the bytes). Those make for very easy to write code, but they come with a few issues, but in general they are simpler and give better behavior than null-terminated strings. However, as for a bit of a historical bagagge, it seems we got used to null-terminated strings and just went on with them.
Only in C, even C++ has since the early days adopted proper strings on its standard library, initially the compiler specific ones from the early 90's, then the standard one.
