People go over the handlebars on braking because they use the rear brake, or are not properly braced on the handlebars. If you use the front brake (and brace properly) there is little practical limit to braking force. You are more likely to skid the wheels than go over the handlebars.
As an aside, it's weird that in the bicycle world we talk about disc brakes vs rim brakes since they are all disc brake systems (in a rim brake, the rim itself takes the place of the rotor). I don't think I've ever seen a bicycle with a drum brake :)