I don't think I 'judge' people on what they do, and I certainly don't ask people outright what their job is. I suppose I say something like 'do you work?' (Not judging either way). If they do say what they do, I try to ask intelligent questions about their job, but if it's obvious they don't want to talk about it, I shut up and we talk about something else instead.
Inevitably, though, you get a impression of a person by their job. Lawyer, accountant, Armed Forces, teacher, engineer, and other professions shows that someone has qualifications beyond school, and you can converse about their training, etc (for instance I have family members who are lawyers, accountants and ex-Forces, so may have something in common in that respect,) or if not professionals, can ask about things like where they are based, and how they got into their job, or whatever. Just being polite and making conversation flow, really.
My ex was an Accountant. We were at a wedding once when someone asked him what he did, when he told them they just said "Oh well someones got to do it!" Which was incredibly rude and stupid - ex was really insulted.
I don't look anything like the 'typical' person people would imagine for someone doing my job (I'm female for a start), and I get instantly judged so tend not to say what I do, beyond a vague description. If pressed I will say what I do, but hate the 'Wow, really?".
Was sitting at a dinner recently, next to someone who did the same job as me. I knew about him (my husband told me), but he didn't know about me.
Because I am a fairly small, innocuous-looking female,(I suppose) this rather boorish, loud-mouthed chap just ignored me for the whole meal and never once tried to make conversation. Had he done so, we could have had a very interesting chat about our jobs, but he had obviously made up his mind that I must be boring and dismissed me. It made me feel stupid and insignificant, and I made a note to myself to never let other people feel like that!!