Participation in TRSA services is completely optional. The depicted airspace is all still class E, and you can fly straight through it sans radio or transponder without violating any regulation.
Obviously, if you do talk to them, they can provide radar services, but this is no different from any other class E airspace owned by an approach facility, including (notably) the class E above and below the depicted TRSA boundaries.
So, why bother showing it at all? And even if there’s a reason to show it, what’s the point in such complex configurations that have zero impact on either pilots or ATC?