Sometimes well-meaning individuals question why I would ever want to have Alanna in intensive therapy for 30 to 40 hours a week when she is currently receiving only 15. I have heard comments like, "shouldn't she just play?", or "won't she get dependent on her instructors if they spend so much time with her?"
I think this stems from a misunderstanding of what autism is and how education treats it. Individuals with autism are completely learning disabled. Most of the time to get started you have to draw them out of their world long enough to even get them to interact with you - this often requires intervention from an occupational therapist to deal with sensory problems. Once a child with autism has some sensory regulation (whether through providing needed stimulation or making an environment tolerable for an over-stimulated child), you have to get them to attend. That is, be able to look at you and pay attention to you for more than 0.2 seconds.
Once a child with autism can attend a little, they can start to learn. But they typically have zero imitation skills, receptive language, speech or expressive language. They have motor impairments. They can lack ability to process tasks cognitively. An autistic child's ability to learn from their environment is essentially zero. So any attempt to allow them to play is likely to result in non-productive self-stimulatory behaviours, like jumping, bouncing, running around, staring at lights, flowers, etc.
Alanna after six months of therapy still has the speech of a ten month old (she is almost two and a half) and the receptive language of perhaps a 13-14 month old child. Socially, she is perhaps in the 16 month range. She is catching up, but she is so far behind. Kids with autism can't play. They have to be taught how to play, just like everything else. Most time on their own is dead time, wasted time. As they acquire more skills and catch up, their "alone" time becomes more productive and the self-stimulatory behaviours can decrease.
Kids with autism need intensive intervention. If they don't get it they may lose skills until they are so developmentally behind their chances at catching up are greatly diminished. Sure, they need rest - time to not think and to relax like the rest of us. But most of their waking hours, like most typical kids, need to be doing very specific educational activities designed to help them learn, because they just can't on their own.