It took me going to a UFC PPV in Vegas to realize that the time is actually based on Las Vegas' time. I'm similarly in the East Coast so used to the 10pm PPV start time and the event ending sometime around 12:30-1am. But in the West Coast, the PPV starts at 7pm due to the time difference. That means by 10pm everything's done, and you (and the fighters and what not) can still go out to the clubs, bars, casinos, etc. with plenty of time left on Saturday night.
The fights are designed to end and seamlessly transition into the rest of the Vegas night life. Which honestly yeah, was a blast not having to decide on one or the other. You're able to go to the fights/watch them, and then still enjoy the rest of the night without having to choose one or the other like you do with the 10pm start time.