Many 3rd parties have the stipulation that they will only reimburse if you hold the CCC. I do all my own billing and it's in my contracts with many insurance companies (I do business in IL).
I am aware of the changes the AuD brought about from the M.S. I know many of the AuD programs in IL require a course in language development of some sort. Northern Illinois University, in particular, has the AuD students take the grad level language development class along with the SLP students. It is also imperative that undergraduate students have sufficient hours in both audiology courses and speech-language pathology courses as pre-requisites to graduate programs. This is evidence of educational overlap between the two professions. I've already outlined professional overlap of treatment areas in a previous post.
The CFY is not a part of a formal education process at any university. It's completed AFTER graduation and is usually completed after 9 months of full-time work or 18 months of part-time work. You can refer to the ASHA website for more detail. I completed mine in New Zealand after I finished my M.S. under the guide of an American SLP.
As an employer and in discussions with other employers, they do not (and I would not) hire audiologists OR SLPs without their CCC or in their CFY year. It serves as a measure of added competence in the Communication Disorders profession. That does not mean that all employers require the CFY/CCC, however more require it than do not. If AAA offered their own type of CFY/CCC credentialing, I'm sure it would take the place of ASHA (and would be fine with most if not all employers). As of now, it's not available, so the default is the ASHA CCC. As a side note, SLPs have the option of also not obtaining their CCC/SLP credential, however employment is limited for them. Even obtaining malpractice insurance is hard without CCC endorsement.
Also, while most states do not require the CCC to obtain licensure, reciprocity is granted much easier if you hold the CCC in lieu of reporting Praxis scores and evidence of graduate clock hours. At least this is the case in
IL and surrounding states. Some state agencies (such as Mississippi State Board of Education) give salary increases for holding a CCC. See
here
If you are a student, as your user name suggests, you'll find out soon enough when you enter the workforce the benefits or no benefits to having the CCC/A if you do or don't decide to pursue it.