I may have missed this in the existing discussion, but one thing that bar ends and the briefly fashionable aero bars (I even saw them on mountain bikes occasion

I may have missed this in the existing discussion, but one thing that bar ends and the briefly fashionable aero bars (I even saw them on mountain bikes occasionally) have in common is that you have to move your hands to access brake levers. In a panic stop situation you simply don't have time for that. The bar ends were for hard climbs, and the aero bars for time trials. Not for general riding. Luckily both have gone out of fashion.