I agree that that is what actually happens in most cases. However, the reversers are initially more effective than the brakes on many airplanes in normal operations.
Depending on the brake system, there may be little or no brake pressure applied if full reverse thrust is used immediately after touchdown (e.g., 747 using Min [Classic] / 1 [400] Autobrakes). Use of brakes in lieu of reverse at high speeds in the 747 Classic will almost always lead to overheated brakes.