Because they are limited maybe?
And everyone trying to get the best character he can get for his style. Its all about what suit your style.
Sonya was pretty okay in Mk10, and Scar was playing multiple character in MK10. Same for Tweedy and this is obviously for a reason.
Sub Zero and Scorpion maybe annoying to the mass, but its obvious at top level they are not that good.
Both have limited combo option, its easy reactable, and its easy to play against them. There is not much you need to be aware vs them.
Against Sub Zero and this is his Dead of Winter variation only you have 1 OH that you need to be aware of and that is it.
The same thing with Scorpion and teleport.
Pro players just knows how to play against this characters and know how to react against this move and thats why they dont have problem against them.
And btw just because Sub Zero have 6f d1, doesnt mean its good. It has 16 recovery, HA is 9 and its -6 on block.
Wanna compare it to a Geras one ? 6f, 13 recovery, HA is 13, -4 on block.
But the problem with Sub Zero D1 and his 1,2 its the range.
Most of his move are very easy to punish. His F4 its slow as hell and you can see it from a plane and you can punish this by 4 way.
His B1,4 its slow and most pro punish it by simply crouch and then he eat full punish. Tho its a great move with superb range.
His B3,2 its a good low, but the range sucks hard.
And its all that Sub Zero have.
And the only really dangerous tool that Sub Zero have is his OH, that a lot of people can react to it animation and this move its full punishable.
So even if you react in 50% of the time, you are still in great advantage, because he is going to eat full punish.
And why there is like 10-15 characters that is better than him ?
https://testyourmight.com/threads/subzeros-low-profiling-issues.69579
His Cold Shoulder is mid and its full punishable.
Also just as i said 2 pages ago, his combo are not easy, not easy to convert and most pro are droping them on regular basis. You can watch Buffalo do it often, you can watch Cat do it, and you can regular play him, you know this is on a regular basis and something normal.
And lastly on his KB and FB. His KB are so so. He has one good one on his 1,2,4 8 hit combo. On his back throw, and you wont get the other 2 in a pro comp.
Im talking about Dead of Winter.
His FB is nothing special. Its hard to land on is own, its has very low start up, easy to learn animation and its a full easy punishable. It has low-profiling and you can dodge it, by d+hit.
If you dont know how to play and or punish vs Sub Zero, go to KombatAcademy there it its explained pretty well and how is it .