Apparently the experience can vary greatly, depending on airport and possibly from were you are from.
I suppose the passport scan (if you are a potential risk-category passenger) triggers a flag to the officer that causes him/her to ask more questions.
And I wouldn't be surprised if the immigration officers have a great deal of leeway to ask more questions on their own initiative, if they don't like the look of you.
It is possible you don't get an interview at all (or it is so short you don't recognize it as an interview).
My personal experience going to the USA 11 times in total on ESTA between 2005 and 2018. 7 times for work, 4 times for holiday:
I never got any real interview. Purpose of visit was asked 8 times and 3 times not even that.
First time was on holiday in 2005. Arrived at LAX (direct flight from Europe). At immigration the officer just asked me "tourist or work?", I replied tourist, passport was stamped and I was through.
I was asked for my staying address only twice. Both at JFK, New York, on a business trip.
In Chicago (O'Hare, been there 3 times for work) I once was picked to have my carry-on luggage examined immidiately on getting out of the plane (before immigration and getting my suitcase from the conveyor). They did that on about 15 passengers from that flight. All men between 30-60 years and traveling alone. They must have been looking for something very specific.
But I didn't get any additional scrutiny at immigration (except for the usual "purpose of visit" question, that I also got on my 2 previous visits to Chicago).