Why can we use static simulations instead of dynamic when simulating spur gears?

I can't find any reasonable explanation for this question except about saving time and computational power. I need physical explanation why we can do so. thanks in advance!

2 Answers

One difference between static and dynamic gear sim is that the stress areas will be concentrated about different regions. For example, static sim results in stress to the tooth contact point, whereas dynamic sim stresses the whole action line.

Static for non moving objects, and gears are normally transferring power while they are moving against each other teeth so designers use dynamic simulation to study the load at each moment.
However there are many equations to calculate the dynamic loads during the design without using the simulation methods which can be found in the gear design text books.