In my experience, it's just to hire the people that got passed over by other companies but still have some skill. You dont have to pay as much and they might also be more likely to stick around longer if they have trouble interviewing at other places.

I'm stuck in my job and I get paid less than people with lower tenure and credentials. Due to a disability, I don't have the social/political skills to get promoted in my org nor feel comfortable job hopping. It's funny though because every team I've been on has had managers or TLs telling me things that equate to 'you should be at the next level' such as "if you were preforming at this same level on another team you would probably be promoted". I had an interview internally recently and was told that I "found more errors than was expected" for my level.

So yeah, get disabled people like me so we are less mobile, work above our level for the technical work, cost less, and can't get promoted easily.