"genuinely passionate about making things better (at least in their estimation)"
and someone who is
"judgmental and self-absorbed in their motives"
Based on this three line exchange?
Starting a conversation with a question like that means the other person will have to reflect it back to you, which means you get to answer however you like. If the person wasn't self-absorbed, they could have answered like "I want to be helpful to others" or something along those lines.
It's not like the idle "So what do you do?" which can be an intentional challenge but usually is idle and innocent.
It's rude and almost certainly caused by self-absorption and self-importance as they said.
Any conversation could randomly wander onto a topic where the question becomes topical, so it's not that the question can never be asked legitimately at a party, but it's not normal.