I cannot for the life of me understand that question.
This evening, I saw someone I only barely knew. I mean, we've talked a couple of times, but that's it. He said hello, and then asked "how are you?" How do you expect me to answer that question? The only way I could possibly answer that question is by saying "good" (yes, I know that's grammatically incorrect, but so is 'gonna' and that's not disappearing anytime soon). Even if I'm not good, why on Earth would I tell someone I barely know that? They would ask 'why' and then I would have to explain some personal story that they probably would rather not know.
Not that I have any reason to say I'm not doing well to that question. I actually was 'good' when I told them that. It's just something I thought about after I was asked that question. I completely understand if a close friend asks me 'how are you,' because I know them well and I would be able to honestly respond.
Same thing with what's up. Actually, not really. I still have no idea how to answer that question. All I ever say is "eh". Seriously. Hahaha.