It's ridiculous really. What is written down can be interpreted. The refs then get guidance, which can be updated throughout a season on what, for example, might be classed as handball. This can differ depending on the level, league or competition, and country. Each decision then is subject to trend and opinion, and can be often justified either way leading to no real culpability. This then leads to fans and pundits, and often players, feeling hard done by because one week it goes one way, and the next the other, and both decisions are correct in that they can be justified.