Well I think that's actually true for alot of people and that's because human beings are generally always more concerned about themselves than others. People tend to genuinely want to know how you're doing sometimes but will turn the conversation back into a discussion about themselves.
This kind of behaviour is actually quite common with people who are self centered and because of this nature, they themselves don't even know when they turn the conversation around and make it about themselves. In this present time and age, It's actually very rare to see a person that will ask about you and actually have the presence of mind to keep the conversation focused on you because everybody wants to be an intellectual and everybody is just roaring to get a chance to tell everyone their opinions and views on life.
I've also found that it's people who are generally more concerned about others than themselves that often get trapped in conversations about another person when the initial question that was asked was about their own well being. The truth is that we have selfish people everywhere and most of them have no idea that they're selfish in the first place.
There's also the fact that today alot of people live dual lives, one life online and then their real life, so it's difficult reconciling the two when you're supposed to living a certain way as depicted by your online life but you aren't in real life. Some people have portrayed themselves as strong and independent online and as such nobody really stops to ask if they're ok and I guess if nobody stops to ask them how they are, asking someone else how they are and turning the conversation to a discussion about them is the only option they have.
You have to understand that every human being just wants attention and some of us will go a long way to get it. I'm sure people don't intentionally ask how you're doing just to drop their own baggage on you, it's probably more of a subconscious thing which they dont realise so don't hold it against them. I've personally decided to listen to people when they make the conversation about themselves and then let them know what they did when their done talking, that way at least they become aware of their habit.
I actually realised this whole thing a very long time ago when I noticed that I'd never let my friends finish telling me about what their going through, I'd just butt in once I heard something similar to what I'm going through or have experienced. From that point, I'd make the conversation completely about me and it wouldn't go back to the person who I actually came to check up on.
I learned to consciously remind myself that every conversation isn't supposed to be about me and listening for the most part is better than talking. So that's what I do now, regardless of what I'm passing through, if I ask you how you're doing, then until we've both completely discussed your issue then I'm not going to bring up anything about myself.
I hope this helps.
I have noticed that a lot of people do not really mean the question when they ask, and many simply do so out of courtesy. Such people will not likely Pay too much attention to any answers provided and may quickly shift the focus of the conversation to them.
People who act this way do so for two major reasons (in my opinion): Ignorance and selfishness.
Many of us who ask "How are you" now do so because that is what society expects from us when we see one another, and it has become ingrained in our characteristics without there being a need to reflect on the question in itself and always be willing to genuinely show interest for the persons welfare when they respond.
Secondly some people are inherently selfish and have a way of making things all about them. Such people should be avoided in the long run, especially if it is proven beyond doubt that they really are self centered