Is that all petting a cat amounts to: You doing the grooming work with your hand so that cat doesn't have to groom himself?

I don't even know how cats think it's cool to take care of the whole body with just a tongue.

How do they know they got the whole thing done like we do when we take a shower?

What about the parts you can't reach?

Doesn't a cat neck and tongue get tired?

Do you do a good enough job, as per the cat's standards?