Contrary to popular belief this bar has many uses. You can do a bent over row to train your lats (large muscles of the back), pushups (chest), squats, stagger stance RDLs, RDLs, pushpresses, and a host of others.
Most commonly this bar is used for the squats/deadlifts and why not?! The Benefits of doing so are:
Less stress to the lower back than a Deadlift (since weight is held at the side)
Less pressure on the top of the shoulders, and less concern with balance than the traditional barbell squat (since you holding the weight to the side)
Is a good exercise to progress to from the suitcase squat as typically this bar allows you to load greater weight