Right Up Front
. My right hand is slightly dominant to my left, and it makes sense to squeeze the front brake - which is the dominant brake - with my dominant hand.
. On bikes that are coaster brake or fixed gear and have only the front handbrake, it likewise makes sense to squeeze the sole handbrake with my dominant hand.
. Using the right hand for braking leaves my left hand free to signal turns and traffic maneuvers.
. This one is tricky to describe, but under some conditions I use the front brake as a "stop rolling" device when quickly dismounting my bike, and this maneuver works best when the front brake lever is on the right.
There are different views out there regarding which set-up makes the most sense, and Sheldon Brown has a nice write-up about it here. Ultimately it is up to the cyclist to determine which feels more natural to them. And if the setup with which your bike came from the store doesn't feel right, be aware this can easily be changed by re-routing the brake cables.