They bought a house. It came with a deed. The deed delineates exactly what rights are conferred. Zoning is not one of them.
Why do we have to bribe people to rescind rights that they never had in the first place?
Why do we have to bribe people to rescind rights that they never had in the first place?
Luckily, none of that will ever happen. You'll get apartments, not warehouses.
So I guess the answer to your question is "because those people bought their deeds under when a certain set of rules were in place, and they are in a position to exert pressure to keep those rules in place". Why would you expect them to act against (what they perceive as) their own self interest?
The answer of "because it helps society as a whole" is a powerful one, but not one that holds enough weight for a lot of people to give up a significant portion of their net wealth / retirement / satisfaction.