In one word - transients
Economists should take lessons from electronic designers. Calculating steady state response is easy, but often it's the transients that will blow the fuse. Abolishing planning will make some people instant millionaires and push others into major debt (yes a house does have very real value when you downsize or move to a cheaper area.) Included in the latter will be a lot of old folks who have no way replace their lost asset.
So how do you get from here to there? Any hint of a possibility that the law might change will lead to instant upheaval and instability. That's not a political problem, it's a real economic effect - just one that most economists that I've read don't deal with.
Add to that, the idea that free market heaven would be established if planning were abolished is nonsense. A few big companies would carve up the whole thing between them, take control of the vital transport links and (as usual) those that shout loudest about the free market would be the ones working hardest to fix it in their own favour.
Of course when we had few controls, what happened was that people built to take advantage of the existing often state-established transport networks, and the state scrambled to keep up with water, sewage, schools, hospitals and so on. Not an ideal model, but hard to work out how to replace it without some ... planning.
And no, I don't support rent control in the least - I'm old enough to remember its dire effects in London.