I have never encountered that question, then again I haven't applied to that many places. Aside from coop positions in university I have only applied to the one job I now hold (I wasn't even entertaining the idea of not getting the job so I didn't bother applying anywhere else
).
I would say that they ask the question because HR is, as a general rule, evil (sorry String, nothing personal). If they were going to pay you 50k/year and you put that you expect 45k... they'll pay you 46k. Look, they just saved the company 4k/year, made you feel great cause you got more than you expected and all it took was 1 question on an application.
In the environment I work in labour is classified by letters. A labour being that which directly contributes to the manufacturing of our product, so the production guys. They are the most important because without them you aren't building the product so you aren't making any money which is the ultimate goal. B labour is the maintenance guys, you don't need them all the time but you do need them cause if the equipment goes down they have to fix it or you are back to not making any money. And so it goes through C and D labour, engineers and such being in there. The people in my office usualy venture to guess that HR is somewhere around the T, U or V labour range - 0 value added.

I would say that they ask the question because HR is, as a general rule, evil (sorry String, nothing personal). If they were going to pay you 50k/year and you put that you expect 45k... they'll pay you 46k. Look, they just saved the company 4k/year, made you feel great cause you got more than you expected and all it took was 1 question on an application.
In the environment I work in labour is classified by letters. A labour being that which directly contributes to the manufacturing of our product, so the production guys. They are the most important because without them you aren't building the product so you aren't making any money which is the ultimate goal. B labour is the maintenance guys, you don't need them all the time but you do need them cause if the equipment goes down they have to fix it or you are back to not making any money. And so it goes through C and D labour, engineers and such being in there. The people in my office usualy venture to guess that HR is somewhere around the T, U or V labour range - 0 value added.