Thusly summoned shall I speak to ye inquirers...
What's going on is that the prevailing feelings are this... 1) Summer. There is a lot to do during Miami in the summer. 2) The Heat are pretty much expected to make it to the ECFinals with Pop'n Fresh and Dwayne Wade. 3) The Wiz are considered a barely playoff team (fans here have a paradoxical relationship in which the expectations of success are set at Laker standards while the expected possibility of failure is positively Grizzlies-in-Vancouverish, meaning they are alternatively too afraid of the Heat choking a series away and yet expect the Heat to lay waste to the Wizards. 4) The Miami curse. Fans here do not care about sports unless a championship is involved (very "unknowledgeable" fan bases; mainly know what the newspaper tells them, few message boards, etc. etc.), which the nation has embarassingly seen with the Marlins, the Panthers (NHL), 'Canes (UM), and occasionally, even the 'Fins.
Basically, there are a collection of wussy reasons for the lack of fan support in this city. Demographics, economics, and realistic expectations all read negative for fan support in Miami.