I suspect it's more because companies can't chose when they have to expand a team. If they need 5 new devs and they need them now, they are in a weak position w

I suspect it's more because companies can't chose when they have to expand a team. If they need 5 new devs and they need them now, they are in a weak position when negotiating salary. Publicising that a new unproven hire is earning more than existing proven staff is simply going to cause people to leave, which is even worse for the business than not hiring new staff.