Apart from it looking nice. Having a good set of glutes is essential for good daily function and integral in playing sports.
Reduce Knee Pain
Your glute muscles create pelvic stability. This is important because your legs function in a closed chain. This means that if something goes wrong at the ankle, it can cause imbalances at the knee and further up the leg at the hip. The same can occur if an instability arises at the hip, it can lead to excess forces on the knee and ankle. This can lead to knee discomfort or pain. Instability at the hip can cause excessive medial rotation of the femur, which in turn creates lateral patellar tracking. Lateral patellar tracking is a common source of knee pain for many individuals.
Reduce Back Pain
Your glutes are responsible for hip extension, and also its reverse action. When the feet are fixed on the ground, the motion your glutes assist with is raising the chest up from the ground, like as in a deadlift. Therefore, strong glutes are essential to lower back health, since they assist with my pelvic and trunk motions as well. When your glutes are strong, you have a stable pelvis and better support for your lower back, so any load can be more evenly distributed through the lower back
Increase Power & Athletic Performance
It is obvious that the glutes are essential to many athleteic activities: acceleration, jumping, and even heavy lifting. It goes without saying that the glute maximus is one of the largest and strongest muscles in the body, therefore it has a lot of influence over the explosive nature of an athletes performance. If you let your glutes get weak, you may find yourself less powerful, and efficient as some of your competitors.