There is no longer a reason for Yasuo not to have a mana bar...
Not to long ago, champs with other resource such as fury/rage and energy, did not have a mana bar. I always felt riot did not give them a mana bar because it would add too much clutter along with their health bar and their resource.
3 bars floating above your champ kinda seemed like a bit much. But with the introduction of Jhin, we had a champ with 3 bars to manage. Health, mana, and bullets.
It has proven to no affect gameplay or decision making....
So my question is, why should Yasuo not have a mana bar and abilities that cost mana?