At longer distances it doesn't take much swivel to cover a running animal, and even one that is walking it's easier to have a pivot point than scrape the legs through the dirt. For still targets, assuming what you're aiming at has a better looking buddy appear 20 feet to the side, pivot instead of fight the bipod.
I've never personally had a pivoting bipod, but have had to readjust mine several times for varying targets. The most stable position may not be perpendicular to your target. I can see the utility.
