When every movie has Optimus sit out of a good chunk of the finale because otherwise he'd just do this all the time. Like seriously Optimus in every movie, after doing something really cool usually involving killing a big threat is removed from the fight so then he can come back and kick even more ass. Outside of the first movie where he doesn't do much once he comes back aside from just get his ass beat by Megatron. All of the bayverse movies do this... and I love it.
