Originally Posted by graywolf

You go back to the 1950's and earlier, and you will find a lot of bicycles, and motorcycles, that were not standardized. Sometime in the 1960's the Feds (USA) passed laws about where the brakes, clutch and gearshifts were supposed to be. In case you are wondering, if you bike shop puts the front brake on the right, they are in violation of federal laws (sort of like disconnecting air bags); it is another one of those laws that apply to manufacturers and dealers but not owners.

And, the rear brake is the primary. The issue is controllablity by a non-expert, not braking power (the laws do not even require a front brake on a bicycle), front wheel skids are dangerous especially in traffic.