This is because they see their mental illness or disability as part of their identity, not as something they need to struggle to overcome.

This is, IMO, one of the biggest (if not the biggest) issues today. Pretty much every aspect of society is honed in on this. You need to find where you have victim points, and you need to keep harping on that and how that makes you special. And people are so focused on why they're a special victim that nothing gets changed, improved or accomplished.