Eons ago, I set up my race bike with the front brake lever to the left. Everyone kept telling me I was wrong. I did it that way because when I ride one handed I carry stuff in my right hand, and want the one brake to be the front. I still ride that way.

At that time youth bikes sold in the USA with single hand brake and a coaster brake were set up with the lever to the left, leaving room for the 3-speed trigger (if one) on the right. Later on when the CPSC established bike standards, they were concerned about reports of endos (among many issues) and they mandated that all new bikes be set up with the front brake to the left. Part of the thinking was that this would eliminate a switchover when children moved from a single hand brake to two.

As far as anyone's personal bike is concerned, there's no rule. You may follow my logic based on how you carry stuff (if/when you do) or any other reason that makes sense for you, or simple personal preference.