Though I believe it should be a developer's obligation to build 'neighbourhoods,' that's not really their motive is it? They do construct 'condo apartments' and that is 'it.' Selling units and 'bringing vibrancy to a neighbourhood' aren't the same thing and having a glut of unleasable retail in a building not only increases one's vacancy (expressed as a %), it decreases EGI and therefore one's ability to meet IRR targets and move forward with additional projects.
Unfortunately there isn't a business model for 'city building,' especially in an inflated market like the one we are experiencing now. This is why we should be looking to beef up regulations like s.37 benefits and giving panels like the DRP more teeth. If they could award more height or density on the basis of good design (as is done in Vancouver), you have the ability to incentivize the creation of an excellent public realm. It's symbolic of the difference between planning by administration, as we do here, and planning by vision, which results in a noticeably better product. In the end, they are the ones building the buildings and it's up to us (the city, the public, etc.) to work with them, rather than against them to achieve the best results.