I'm generally against zoning restrictions. But, there's only so much a city's infrastructure can take. Let's say they build another 100k 3 bedroom units, where is all the waste going to go?
Is there a good reason for all of these people to live in one little area? No, I don't think there's a really good reason. Everyone wants to take advantage of what the city has to offer, but nobody actually wants to pay fair market value.