Lot of developers are happy to treat the required ground floor retail as a deadweight loss, much like they do required parking. So income from rents on that space doesn't enter into the proforma, and it's easier to just not deal with it. Compounding the issue is that for new builds, the leasing agent is looking for a stable corporate tenant who can afford to pay the high lease rates. And rather than simply accept lower rents, they are willing to wait. Waiting five years to rent for $100/sf for five years is better than renting for $50/sf for ten year - no buildout or depreciation.