Some games certainly do that and most audio engines will allow the sound designers to add random variations, along with randomly selecting between different sam

Some games certainly do that and most audio engines will allow the sound designers to add random variations, along with randomly selecting between different samples. There is only so much you can do with pitch changes and creative use of filters, and having multiple samples for each sound can burn memory (and sound designer hours) fairly quickly. As you point out there is a wide variance in the technical skills of sound designers (some love playing with the game engine side, some are better at making sounds and throwing them over the wall).