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@BBCWatcher shared was one example where one’s cognitive ability has been impacted in some way yet physical mobility is totally fine.
Yes, one of my former colleagues happens to be in this situation. She's long-term disabled, medically unable to work due to frequent enough lapses in her logical reasoning ability. I'm not privvy to her exact diagnosis, but it's some sort of cognitive issue that cropped up in her 40s. My employer can't keep her on the job due to her cognitive issue, but fortunately she's collecting group DII to age 65. I think 2/3rds of her prior salary is insured. Then AFAIK she has good (or better than good) retirement income security thereafter.
With the current white collared workforce, I see DI carving out a niche of its own to preserve your income from any mental/cognitive disabilities while Careshield protects against physical disabilities.
I think of CareShield Life as providing a "boost" if you need someone to help you get dressed, feed yourself, and otherwise perform essential living activities. Atop/alongside DII if you can no longer work due to disability. CareShield Life is really what the industry would call "Long-Term Care" (LTC) insurance, insurance that helps pay for nursing home care or similar at-home care. Granted, base CSL won't buy a lot of help.
Maybe it'll pay part of the cost of a full-time live-in domestic helper with the right skills.
Also, I'm kind of puzzled why DII is so often considered a "white collar" type of insurance. I don't understand that at all. The only reason I can think of why that perception exists is because higher income individuals might better understand the value of DII (and negotiate employment contracts with group DII for example) more often than lower wage workers. But in terms of financial vulnerability it's the lower wage workers in any/every profession that should be most vulnerable to disability and associated loss of income.