You might be surprised at how close they sometimes get, at a glance. For close up magic it has to be readable at a quick glance (without an app). For some of the cheating it has to "not even be a glance" because you can't get caught looking at the side of a deck.

To be fair, sure most of those marking strategies are approximations designed for a specific trick or a specific gambling game and so don't always need to be 100% of the state information (suit and rank of every individual card). But there are certainly close up magic reasons to have a deck you can find exact cards by marks. Though also to be fair, many (but not all) of those do move the marks to the back of the card with the assumption that you can at least spread the backs of the cards.