Simple and natural is often a result of experience.
For some changing the oil in car is simple and natural. It is after all the most basic of car maintenance. Someone with experience can just walk up to the car, pop the hood, find the cap, find the filter, and start draining the oil pan.
But for those who have never done it would it be simple and natural? They might have to find the owner's manual (or even discover the existence of an owners manual), or google videos or a write up on their particular Year/make/Model of vehicle. Even with those aids they are likely to mess up, spill some oil, forget to put the cap on, or forget to put the drain plug back on the oll pan before adding the new oil, or forget to replace the filter at all.
This thread is one of the best write ups on the changing the oil for new D&D grease-monkeys that I've read.