Originally Posted by FBinNY

lt's clear up the first misconception. Friction isn't dependent on surface area, it's related to the clamping force. There is a benefit in terms of slippage by increasing the torque at the slipping surface, but not enough to justify the effort.

If we go back in history, the real reason for a bulged center becomes obvious. It's so the bar can be slipped through the stem freely and only be a close fit at the center. In this way, the bulge on bars is like the raised crown sear on fork steerers.

The second reason is to increase bending moment at the fulcrum, where bending stresses are highest.

As far as slippage goes, the remedy is cheaper and simpler than forming the bulges. Simply coat the bar clamping area with traction material similar to the traction strips on stair treads. Many already do this, and it's very effective even at low clamping force.

As I posted earlier, I suspect the ONLY reason for increasing clamp diameter is to have something new to sell.