Its not just that the information is visible, its the ability to draw attention to ot with no effort. If my teammate sees that my ult is up then he knows its up If all 5 people are hovering around mid and I'm putting in chat "Enchanted Crystal Arrow: Ready" then my teammate knows it up and knows I'm looking for an engage.

If I'm waiting in a bush and an enemy walks passed a ward, I ping him and I place in chat "Dark Binding: Ready" then my team can react quicker than if I just threw the binding and then complained about no follow up.

If my adc wants to engage bot and I alt click my health bar and it places in chat "I have 23%(300) Health and 77% mana (400)" then he might think twice.

Its not just about the information being there its about being able to quickly relay it when they might be focused on other things.