Uh, let me just start by saying that a “flash hider” is not a “suppressor”. They are two different types of devices. A flash hider is designed to, as the name implies, reduce or eliminate the muzzle flash of a firearm. This is accomplished through various means such as venting the gasses that cause muzzle flash-sideways or providing a place for those gasses to cool and be dispersed before exiting the muzzle. On the other hand, suppressors work by trapping those same gasses and allowing them to expand and cool before release.
While there are plenty of muzzle devices on the market that serve multiple purposes, most flash hiders are designed for a single purpose: mitigating muzzle flash. This is important for several reasons. First and foremost, it can help conceal your position from enemies when firing in low-light conditions. A muzzle flash can easily give away your position, so reducing or eliminating it can be a tactical advantage.