I think the "benefits" for a pure road bike are very minimal. The only things I can think of are - shorter reach brakes can be smaller and lighter, and design wise the frame and fork can be ever so slightly more compact, lighter, maybe more aero. Mainly, I think people designing pure road bikes never imagined anyone wanting wider tires and designed everything with that assumption.

It seems like a lot of manufacturers are making bikes and frames to accommodate wider tires. My Kona commuter bike can take pretty wide tires and pretty much everything by Surly is designed for wider than usual tires. There are lot of options out there.