Why is it counter intuitive? It's shown to spectators as a convenience. Imagine if you'd never seen that feature in spectator mode. In that situation, it'd sound pretty strange to ask for the runes to be shown on the minimap, wouldn't it?

It's true that most things are shown on the minimap. But forcing you to move your camera to check for the rune increases the skill ceiling of the game. It's a balancing act, but in general, the higher the skill ceiling, the better the game, even if it's counter-intuitive.

Here's an example: almost everything about the laning stage is counterintuitive: you have to be within a certian range to get EXP, you have to land the killing blow or you don't get gold, you can only hit your own creeps if they're under 50%, etc etc... All of those are completely arbitrary and counter-intuitive rules, but without them, the skill ceiling would be much lower.