It does not attract more applicants because they won't know about it unless you advertise a specific amount, which then creates other problems. You'd get a flood of useless people if the number is high. Some other people, underestimating themselves, would not apply. You remove the flexibility to hire both junior and senior people because one single pay number can't fit both. Even if you provide a range, you have the problem of pessimists and optimists assuming very different things about where in the range they might fall.