TEACHING TEXTBOOKS - TT is a lot more flexible than a live tutor. You can use a TT in the comfort of your home on your schedule. Most tutors require that you travel to a tutoring center. Also, to hire a live tutor to walk you through 4,000 problems step-by-step would cost thousands and thousands of dollars. A TT costs just a small fraction of that. And you can't fast-forward and rewind a live tutor either.
This Math Textbook Cover Will Make Your Head Explode