A couple of NPR shows have covered this. Disability is a federal program and states (especially poor states) are motivated to get their unemployed people off of state benefits (like unemployment) and onto disability. For one, it saves the state money and it also removes those people from the state’s unemployment number.

https://apps.npr.org/unfit-for-work/

> There's no diagnosis called disability. You don't go to the doctor and the doctor says, "We've run the tests and it looks like you have disability." It's squishy enough that you can end up with one person with high blood pressure who is labeled disabled and another who is not.