Hope they make you happy. That is assuming you already know "C".
That is the whole point. So many ask for C on the '51 and want to skip the "C as a language" step. There may be a small market for a book that taught C from the bottom up on the '51 but which publisher would take a book with a potential sale of 500 copies, especially since it the potential market would insist on it being cheap.

Another point is that to make "hello world" appear on a PC monitor is - for a raw novice - about 10.000 times easier than programming a '51 to send "hello world" through the UART and coupling that to a PC and making the PC process it to the screen.

Erik