It feels to me like these american show masters, who get on stage and greet the people with a "hello, how are you doing" but since he's asking the whole audience, no one answers.
It took me years to get used to people going "how are you doing?" and just walking straight past me. To me, it seemed exceptionally rude - I'd stop, and start answering the question, but the person had just walked on. It took a while to realise that in some places it is just a greeting, and much longer to not have to consciously remind myself about that...