Let me just say that I am not in product management. I am only speaking for myself.
STA failure association messages only mentioned that stations failed associations and did not provide any more information about WHY they failed, so they were just tons of messagest about clients that failed associations. Some failed associations are just based on contention that can be just ignored. Others are for clients that are not even yours, but they were still reported. So you end up with a long list of station association messages, but no real idea about why and if they were important. There is normally not enough information from the controller perspective to give more useful information that would help you determine if there was anything you could do about an association failure.
Client debugging provides much more information for you to understand why a client you are interested in, is not working.