No worries, I’ll try to succinctly explain (it’s 5:08 AM here and I need sleep).
It’s not so much about efficiency. Calling me “a man with mental illness” trivializes the experience and makes it sound like you can separate the malady from my person. You can’t. Being, as in my case, bipolar and obsessive-compulsive is part and parcel of my life.
“I could care less” is an idiom, a set of words that is somehow beyond the sum of its constituents. It’s apples and oranges with the preceding.