(I waited until I heard from two more people before posting this question, just to rule out the possibility that was a random act of a rogue airline agent 
)
My co-worker and I were checking in for our flight from Switzerland back to the US. I am a US citizen. She is a British citizen who has been a US green card holder for about 20 years, residing in the Bay area.
The agent gave me back my US passport and boarding pass without asking any questions. He then asked my co-worker a bunch of immigration related personal questions. This is how I remember them:
1. What is your occupation?
2. Where is that company located?
3. How long have your worked for them?
4. What was your area of expertise at your job?
5. Are you married?
6. How long have been out of the US?
My co-worker, a well-seasoned int'l traveler, was dumbfounded because no airline employee has ever asked her such questions. The airline agent apologized and said "the computer required to ask me the questions" !!!??? My co-worker was a good sport and just answered them. The airline agent seemed very apologetic and thanked her for answering the questions while she entered the answers into the computer.
I became nosy and asked her "who is asking these questions? the US government or United Airlines?" and she said "I couldn't say"(not sure if she meant couldn't or wouldn't).
The flight was uneventful and when we landed, my co-worker was not asked any other questions, other than the usual CBP chit-chat. She went through faster than I did because the CBP agent who scanned my US passport probably failed typing in high school?(typing with two index fingers only)
Like I stated at the top of this post, I asked another friend and a former co-worker, both green card holders, to see if they've ever experienced anything like this. Apparently they both have. One was NH at at Narita and the other one LH at Munich. The friend is Australian and the former co-worker is German. They said they got asked similar questions by airline check-in agents within the last 3 months, but NEVER experienced such questioning in the dozen+ years they've lived in the US as green card holders.
So... what has changed and what U.S. agency is making those US and foreign airline check-in agents to ask the question? What is the purpose of such questions?