There are 3 type of martial art sport, every type have different clothing design because their training method also different each other.
Best clothing for fighting sport and martial dance training is loose clothing. For examples are Kungfu outfit, Kuntao outfit, Karate outfit, Kickboxing outfit, Boxing outfit and Silat outfit.
Loose clothing allow you moving, punching and kicking faster, because your muscle more relax and not pressed by tight clothing (in self defense, there is a concept called "Explosive Power" of "Fa Jin", where quick step, fast punch and fast kick are launched suddenly from relax muscle).
By the way, wrestling sport use different clothing design. Very contrast with fighting sport and martial dance uniform design.
Tight clothing like Wrestling singlet and Catch Wrestling legging have different function. Those tight muscle suppressing clothes are used by wrestlers to prevent muscle injury while lifting heavy opponent, the concept is just like calf support and big leather belt used by weightlifters.
For wrestlers, sacrificing their own speed - agility by using tight clothing is not problem, because their sport is more focus on raw power - raw strength.