Because the healthcare system is vast and has many aspects. It also varies across locations.

My son doesn't have classic autism but he has developmental delays, sensory issues, etc. Trying to find providers here in the bay area can be extremely frustrating with extremely long wait times and we have great insurance. Our prior plan was Kaiser and it was just as much of a hassle but in a different way (having to go through a special office to get approval for therapists, etc).