My guess is that insurance companies know they cannot legally deny certain treatments, but they will deny said treatments anyway to cut costs. Many people will not put up a fight and will accept the insurance company's denial. It may behoove you to fight for your rights and insist on treatments. Be a pest. "Write letters, insist on talking to a live person and not some voicemail. Make sure anybody you talk to has the authority to authorize the treatment you need, and if they do not have the authority, insist on talking to somebody who does have the authority. If the treatment you need happens to be particularly expensive, it might be worth it to get a lawyer.