Its a good point about hotels vs apts........I hadn't thought about it from that perspective. However, I think there are enough hotel chains that will build hotels if the market is there. And cities talk a big game when it comes to conventions but from what I read, convention centers are overbuilt in this country and tend not to be very profitable:
http://www.citylab.com/cityfixer/201...-centers/2210/
The convention centers may not be profitable per se, but it's the spillover effect that is important. Conventioneers spend money at hotels, restaurants, shops,and for entertainment, transportation, etc. Also, consider the excellent PR effect. If thousands are impressed with DTLA they will be most likely to return on their own when vacationing. They are likely to tell friends about their experiences, and so on. The multiplier effect is enormous. Why else would cities' vie for convention center domination?