Why do they implement price ceilings on new apartments?

‌In my opinion, the only reason is "envy"—they simply cannot stand to see union members making money.
Why do they maintain such a system..?
1. It is a negative factor for revitalizing reconstruction projects.
2. It concentrates development profits into the hands of a tiny minority of general subscribers.
Why do this..?
Is seeing union members make money really that hard to stomach?
Or is it being maintained so that the children of politicians can win the subscriptions?