They are business like. I think it can often come across as rude and abrupt.
It is hardly a warm welcome, and it is the first impression any first time visitors get of the country, which can be a shame as it is off-putting.
The trick is to just suck it up and answer the questions, nothing else.
Once through though everything is much better in my experience. I've enjoyed our few trips over there, and would go again.
Mind you, I remember being questioned about whether or not my then two year old daughter had ever been refused leave to adopt a child in the USA. I never did work out what that one was about