Being proficient in the skills you need to do your job is important.  It does not matter what your job is you have to have the knowledge to do your job properly.

With the MTTC study guides, you are going to learn what skills you need to work with to successfully pass the exam and to do the job.

You need to be proficient in specific areas to do the job as a teacher well.  That is how these study guides prepare you for the job that you want to do.  They will show you what areas you are expected to be most proficient in.