If you're in New York City, this may be related to rules on rent stabilization. Rent stabilized apartments can only raise their rent by a small percentage each

If you're in New York City, this may be related to rules on rent stabilization. Rent stabilized apartments can only raise their rent by a small percentage each year. These landlords likely want to be able to raise rents quickly if the rental market heats up, so they raise the "actual rent" by the maximum percentage each year but then give a concession so that they can actually find a renter.