Two reasons, though both are closely tied:
-Lack of real life practice
The only reason why people even bother with unrealistic techniques is because they never really spar against competent stronger opponents.
The only martial arts that are worth a damn are those with constant full contact sparring. To learn how to fight you have to fight.
This nonsense of doing forms and katas is pretty, but useless.
What happens is Joe goes to kung fu class, learns the crane fist and whatnot, repeats that dance over and over again and in real life finds out that it doesn’t work against an angry adult man who’s hitting him in the face.
That’s it. The top 6 martial arts I put there are all realistic martial arts which focus on full contact sparring from day 1. They are also SIMPLE. The tools are simple and effective, but they are trained over and over again.
You know how many punches there are in boxing? 4. Jab, straight (cross), hook, uppercut. That’s it. No “dragon whips its tail” or “iron tiger claw”.
Then you learn them perfectly and you punch bags, speed bags and other people 2 hours a day, 4 days a week for 4 years and guess what. You learned something.
Transposing it to street fighter, since this is the topic: two guys bump into street fighter. One sees a gimmick character , Dhalsim, and goes into training mode and keeps hitting a dummy every day. Has no idea how a fight goes.
What happens? As soon as he fights his first match against Sakura, she gets up in his face and he has never seen a frame trap before, has no idea how fast those hits come at you , nothing. All he has is how he thought things would go. Oops.
Another guy picks Fei Long. Solid character, SAFE, mobile, strong pokes. No gimmicks, just practical usability and safety. Spends an hour a day on the training room then 1 hour in Endless matches.
That’s the difference. Unrealistic gimmicks without any real life experience vs. practical, true and tested violent simplicity put to the test every single day against competent opponents.