This is my question as well, seems like a boat load more work than writing c to a file and calling gcc on it.

One thing I can think of; if the language you're implementing has exceptions, you'd have to implement these the naive way wiht setjmp/longjmp if you target c. Supposedly if you used gcc in the way this article shows, you could use gcc to generate "real" excpetions.

If the author wants to show how to write a front end targeting GCC then writing a translator to C would not do that.

It is an educational exercise.