It is not that you aren't engaging your gluteal muscles ever- because when you are standing you obviously use back-side muscles. The medius and maximus gluteal muscles have more than just one plane of motion that they perform in. If the lateral plane is not worked, then the muscles do get lazy. If the sagittal plane is mainly used for exercise (like runners), the hips have less stability so the joint above (low back) or the joint below (knees) take the injuries during the compensations at the hip. Even worse, we sit SO much more than our body was made to sit- that the tighter front hip muscles regularly disengage the back hip muscles. So before getting compound movement work outs (squats and deadlifts) activities at the gym, turn on the gluteal muscles- especially gluteus medius with these five movements. You will get more for your effort. If you have knee problems, strengthen the hips with these five movements. If you have poor balance, do these five activities. If you need a good warm up activity, do these five activities. Get the point? Turn them on!