If it was exactly 3 photos per shutter press, they were most likely using bracketing rather than simple burst shooting. Bracketing can be used for a number of different purposes, but the concept is that it takes some aspect of the camera and changes the setting between shots. Exposure, Flash Power, White Balance, Focus, etc can all be varied slightly to give a range of shots. HDR photos also are typically generated using an exposure bracket.
Simple use of continuous burst shooting can also be useful for making sure you get a good image. Since you can't control things like when the speaker blinks, one shot might end up catching him blinking, so taking multiple shots gives a better chance of getting a good shot.
I personally don't use bracketing very much, but my camera is ALWAYS in high speed continuous mode. I may only take a single photo at a time, but having the ability to take more quickly is valuable to have. With practice, you can control exactly when and how many photos you take while using a good high speed shooting mode. (Plus it's kind of entertaining to hand your camera to someone and have them accidentally take 2 to 4 photos and wonder what the heck just happened.)