Some champions that use mana: 
Some champions that use a 'special' resource bar:
Some champions that use energy: 
And then there's these: 
So why do these two not have any sort of resource bar?
Swiftstrike44 votesManaless champions are all different. Those bars indicate different things related to their kit, not necessarily them spending a resource.
Dovahkiin4161 votesMANALESS! That's the word I was looking for! Not necessarily 'resource' bars, but at least they have a bar other than health.
Unlike or
Mr Broken Wings3 votesThe reason for that is that the manaless champions got bars that fit to their playstyle. Katas kit is based on resets and low cooldown resets, you dont want to give her a bar in that case because mana is no option and energy gates her playstyle. Imagine riven or kata getting a ragebar that makes them stronger, this would be stupid as fuck lol. Riven got a bar on the pbe once but they didnt implement the edge bar because it would have buffed her horribly and yeah, she doesnt need that.
Dovahkiin4161 votesI just think they should at least have a mana bar, they are both quite ability reliant. more so than
It would maybe make laning phase/early game a bit more tough, and give champions a chance to maybe get a kill off of her early. It would be a nice counter other than hard cc, or being a tank.
As for , I just think she can play way to safely early with her kit. Use her Q combo, then W, and finally E away to safety. It would make her be less aggressive early, and make her recall to refill mana. Instead of staying in lane and out-sustaining you because she can safely trade, and win against you.
Mr Broken Wings4 votesI just think they should at least have a mana bar, they are both quite ability reliant.
It would maybe make
As for
rivens and katas earlygame are weak enough already lol, they dont need to be even worse then they are right now
ÂzaIea2 votesKatarina already has the weakest laning phase in mid lane. What else would you want?
Katarina's weaknesses are
EDIT: Also you do realize Yasuo does not have a resource right? The little mana-bar-like-thing can be considered as the cooldown to his shield. It is almost the same as Vlad's bar being Q cooldown. except it refills with movement.
Dovahkiin4161 votesWhen I played often I found her laning phase to be incredibly easy.
Once you hit three just Q, E, then W onto them to trade. Wait for cds, then repeat
Then once six comes, if they have no hard cc, and were too dumb to recall when they have 1/3rd hp. Just do Q, E, W, and finish them with R, and an ignite for safe measure. If they weren't already dead.
ÂzaIea1 votesYou are playing in Bronze though. Most Bronze players do not understand how to trade properly and it is easy to abuse, especially as Katarina.
Katarina scales directly with the game knowledge of the person using her in higher elos, and indirectly with opponent's ignorance at lower elos. That is why she is considered a noob stomper.
As soon as you play her vs opponents that know how to punish you for playing that champion, she becomes insanely hard to play.
Dovahkiin4161 votesTrue that, game knowledge OP.
ÂzaIea1 votesThat is actually how Assassins work in general. They have their skill cap. But to play an Assassin effectively you need a lot of game knowledge. That comes from the fact that they have to wait for the most opportune moment to go in in a fight. But how do you know the most opportune moment without knowing every character's cooldowns?
Dovahkiin4161 votesVery true, there's so much more to league than what meets the eye. half of being good at the game is knowledge. Something I exploit in Bronze haha
KTAS Phirus2 votesStill balanced
Dovahkiin4161 votesIt just seems like they are missing something to me.
I mean why can't use mana? It would fit perfectly with her. Just simply add %mana restored upon a kill or assist to her passive.
KTAS Phirus1 votesSimply they are both champs that must poke to be able to kill someone and if they go in they have to all in and kill quick or die, so the fact that they can poke slightly without going back. Moreover they have both bad early phase and that helps
Swiftstrike42 votes
also has no bar.
They don't really need one unless it were to attach a resource.
The only thing I could think of for would be a bar that fills up after she gets a reset from a kill. But it would probably immediately disappear because she would immediately use her skills after the reset.
Dovahkiin4161 votesAh I forgot about
I guess he doesn't really need one, as he is built to out-sustain and be a mega tank. (or build crits if you're a dick)
Maybe a bar similar to 
It would give him crit chance by auto-attacking, and be expended upon spinning?
ÂzaIea1 votesIf anything, Kat needs a Yasuo-like thing that shows how long she has left to get a reset from people. But that is not a resource haha.
ReZisT Lust2 votesYou forgot kled
Dovahkiin4161 votesDoesn't he have a bar similar to 
?
But when full it inspired his Skaarl, or however you spell it, to return to battle?
ReZisT Lust1 votesNo its not even "kleds" bar its actually skaarl working up the courage to come back into the fight which is nothing like gnars
Dovahkiin4161 votesI mean the fact that once it's full, your character model changes, as do your abilities. In that aspect it's similar
ReZisT Lust1 voteseh i guess he loses his er while unmounted too
ScissorsNstuff1 votessome champs have no resource
its just a matter of design
if you list every champ without a resource though youll find they follow certain design patterns