It is the engine for everything that involves standing up, jumping, sprinting or picking something off the floor. Most desk-bound clients arrive with it undertrained relative to the quadriceps, because sitting shortens the hip flexors and nothing in daily life asks the glutes for much.
Two lifts cover it: a hinge (Romanian deadlift, conventional deadlift, hip thrust) and a knee-flexion movement (leg curl, Nordic curl). One of each, twice a week, is the baseline.
A rough check on balance: a client should be able to Romanian deadlift for reps at a weight close to what they back squat for the same reps. If their squat is 100 kg for 5 and their RDL is 60 kg for 5, the back of the body is the limit.