I also think you're displaying little imagination about the usefulness of salary as information. For example, OKC has many questions about (and another sidebar slot for) persons' interests in/preexisting status regarding children. There are questions about marriage, etc. - lifestyle stuff. Salary is a factor in what kinds of lifestyles are available!

For young people, I doubt that “salary now” is such a strong factor in “kinds of lifestyles available by the time I'd want to start a family”. (Here in Italy, ISTM that most relationships start when people are still in university or younger, when their salary is zero or close to zero, and most people old enough to make more than $20,000/year already are in long-term relationships; I'm guessing it's not the same in America?)