The question about the role of parents in treatment of teens and young adults has been popping up a lot recently. Typically, it is my experience that parents want to attend or somehow be involved in therapy with their teen or young adult, but feel like it might reflect negatively on them as parents if they are involved (or to even want to be involved).
In a couple sentences, here is how I view the issue clinically. Regardless the child's age, if the child is in some way dependent on their parents (financially, emotionally, transportationally, etc.), the parent can play a role in the individual therapy of their child. In fact, for clients who are 18 or over and still living at home, I insist they sign permission for me to speak with their parents.
I have tried to do this otherwise (ostensibly respecting the "independence" and privacy of the young adult living at home), and found it nearly impossible to make progress with no access to the parents. For clients who are 18 or older, living at home, and want to completely restrict my access to their parents (i.e., refuse to sign permission for me to speak with at least one of their parents), I provide referrals for other qualified service providers. I am certain there are other therapists who feel differently than me on this issue, but I find the lack of access to the parent to be a deal-breaker in choosing to work with a potential client.
To you prospective clients who are young adults and living at home, let me be clear that this does not mean I will record our sessions and play them back for your parents. My general policy is that regardless the fact that you give me written permission to speak with a parent, it will be my intention to check with you before I communicate with your parent. I am well-aware how "going behind the back" of a client can hurt the trust the client has for the therapist. Behavior like that from a therapist is also a good reason to find a new therapist, because trust is at the core of most everything we do, and lack of trust limits the potential for progress.
It is very common (almost assured) that my work with young adults on the Spectrum will be initiated by the parent. There are a lot of reasons for this, but parents are almost always invited to attend the initial session with their children, regardless the age and ability of their child. Indeed, setting goals of individuation from parents and increased independence are common in therapy and not something I would consider a prerequisite for therapy.
One way to look at how society is changing is to think that because children are living at home longer, being financially and emotionally dependent on parents longer, they are developing and maturing at an artificially slower rate. Of course, another way to look at this issue is families are slowly returing to a more generationally-blended model like that of older and more established cultures and societies. Research has uncovered a lot of benefits to the multi-generationally family.