Optimization is usually possible, but it is easier said than done. Often sacrifices have to be made, but maybe it is still a better value per frame time. Sometimes there's more that can be done, sometimes it really is just that hard to light and render that scene.

It's hard to make any sweeping statements, but I will say that none of that potential optimization is going to happen without actually hiring graphics devs. Which costs money. And you know what corporations like to do when anything they don't consider important costs money. So that's probably a factor a lot of the time.