There is a real buzz around Las Vegas when there is a big boxing fight on there, being held in one of the bigger hotels. All of the casinos see a massive increase in traffic, and the amount of betting in general just goes up on the weekend of the fight. Vegas really comes to life around the big fights, and people just get into spending mode very quickly, so everyone looks to capitalize on this.
For example, this year when the Mayweather vs Pacquiao fight was on, the crowds around Vegas grew to record levels, and the amount of money being spent in the casinos on the Vegas strip and sports betting too, just rose significantly.
It is easy to see why all the top hotels in Vegas all want to get the big fights in their location. The promotion it gives them, along with the sell-out of all of their rooms, and increased traffic through their casino is going to add a massive boost to their revenue, both in the short term, but also in the long term too with the amount of promotion they get from it.
Boxing has always been a sport that attracts a lot of betting. Trying to guess which fighter will win, which round they will win in, and how they will win can draw some very attractive odds for the punter. So there is a lot of money to be made by those that get their bets right, and a lot of money to be made by the sports betting companies that offer the bets too.
The promoters of big fights do a great job of building up the hype and bringing people in to see the fight. There is so much money involved in the actual fights these days, that they can afford to go 
all out with their promotion and attract people from all over the world to come and watch the fight. They also sell the television rights for huge amounts too.
But the betting on big fight nights does not just happen in Vegas itself. A lot of people will bet online, and the efficiency of online better has gotten so good now that it is possible to place last minute bets, or place bets in between rounds even. Also, the online casinos have a massive boost in traffic around these times too, as people get into gambling mode and want to have a flutter online if they are not close to a casino.
While boxing is still able to generate so much buzz and hype, there will always be massive boxing nights in Las Vegas. This will continue to see all of the hotels and their casinos doing massive business around this time, as well as all of the online casinos and betting sites too.