What's so depressing about that, and what would you suggest people ask instead? People's careers take up a lot of their time and provide their livelihood, and a lot of people are quite proud of their careers. Sure, things like sleep and diet are probably more fundamental to a person's wellbeing, but it's pointless to start smalltalk with "how much sleep have you been getting?" or "what is your diet like?".

I consider it a clear improvement over its primary competition in other cultures, "Where are you from?" and "Who are your parents?" At least this one, if you don't like the answer you're giving, you have power to change it.

I agree - it's not good small-talk. Since this was pointed out to me (~15 years ago) I've made a conscious effort never to ask people what they do for a living. One friend I knew for a year before I found out what he did (that's a rare situation, granted). If you haven't tried it then I highly recommend it.

In my experience this usually takes the form of "what do you do?" The question irks me because I know that what's implied is the "for work" part, and that in turn implies that somehow, the way I make money is the signature aspect of my being. The assumption is built in to our [American] society of course. My response to this query is always either "do for what?" or a list of things that I do that I consider important (walk, ride my bike, work out, travel, listen to jazz, read ...).