Sparring in combat sports training is only necessary if individuals are interested in participating in the sport or art for more than just a alternative fitness training method. Sparring is a choice not a necessity of martial arts training.
For individuals that want to evolve their sport or self-defense skills, sparring is a recommended! Spar training helps an individual martial athlete's (1) Technical Development, (2) Personal Conditioning, (3) Technical Timing.
Sparring should only be conducted when participants have adequate amount of hours, weeks, or months of training. All beginners to sparring should be supervised by their coach or instructor until they are ready to spar without supervision an experienced martial athlete or coach.
Light or flow sparring is a good way to initially increase one's learning curve. It is important for participants to begin to learn how, when , and where techniques can work for them or how, when, and where they may not. Though, it is important to consider, most techniques can be executed if practiced and drilled enough in an individuals training. TIMING is more times than not most vital in successful execution.
Sparring is not to find out who is the "Biggest Bad Ass" in the gym!! Sparring is to develop individuals ability whether a beginning level student or an accomplished fighter.
Hard sparring should only be conducted by very skilled experienced martial athletes and/or competitive fighters.