They store energy. And not always the good kind. They are a group of bones, joints, and tissues that are a powerhouse for activities like running and climbing. But if you are storing the excess energies of stress there, you may be holding back your potential.
Think of your hips like your upper back and shoulders. Along comes a stressful day, and you may feel like you need a back rub to get the tension out.
You can give your hips a "rub" by stretching them.