it's needed for wide metal so that mechanical stress will be reduced. It will improve yield, but reduce your metal sheet resistance, hence increase voltage drop along the metal
Randy..Just re-check your answer. If "resistance is lower voltage drop is more" it is the case then why do you need to create power grid to lower resistance??
you need to reduce the R to reduce the voltage drop for a certain power consumption, and have less voltage difference all over the design, and the std-cell can have the same "timing" behavior.
and to reduce R, you need to increase the area to transport the current.