Why Do We Need Another Arena?

Talk about a waste of taxpayer money.
From the LVRJ: The city of Las Vegas plans to continue working with Cordish Companies to develop a $390 million downtown sports arena, with the city paying $239 million raised in part by a special tax on downtown businesses.
The terms are attached to a proposal to extend by four months a three-year-old exclusive negotiating agreement with Baltimore-based Cordish, which would contribute $151 million to the deal.
It’s scheduled to go before the city council Jan. 22. If approved, Cordish and the city would have until June 1 to finalize a development agreement based on the proposed terms.
If the development agreement isn’t finalized by then, Cordish would walk away with about $2.4 million based on the initial agreement from 2010.  http://www.reviewjournal.com/news/arena-proposal-calls-239-million-las-vegas-some-raised-through-special-tax
The MGM is building an arena, we have the Thomas and Mack on the UNLV campus, there are numerous other smaller arenas, like the Orleans arena.
So, why does the City of Las Vegas need an arena?  To keep up with Clark County?
This is just a waste of time and money. After all, it's just taxpayer money.