I take the skid plate off on our 100 for an oil change as well because I've yet to get the filter off without getting oil on the top of the plate.....in my opinion an unnecessary annoyance when Toyota gave us a filter window on the 100.
Aside from the desire to keep oil off the truck (and driveway) it's a good opportunity to inspect the engine from below. I wouldn't have found a failing water pump had I not seen the pink crusties around the timing belt plastic which was not visible from above. For most users this is only a 3x per year event and it's just wise to take a few extra minutes to ensure everything is is proper order. This is especially true with an aging fleet. Inspect for leaks, worn hoses, chaffed wires, torn boots, etc. while you're under there.