OP is HR, and this is one of their talking points in the overall denial of excellent raises and bonuses in a competitive job market.
Most people are leaving because they have friends, meaning, they are finding out what their former colleagues are making, at their new employer, and then come to the conclusion of “why not, let’s see what happens.” Then they get that surprise offer, and leave.
The second issue is people are getting more responsibility, for the same pay, because they are having to load up on a former employee’s responsibilities, and GF won’t backfill the position, for “cost savings,” but continue to stress their employees through overwork and no recognition (in the form of monetary compensation or promotion). A pin is not recognition.
That is what is happening on “why people apply/accept outside phone calls.”