Developing a massive and detailed pair of quads not only takes years of hard training, but it will also likely requires a healthy amount of unilateral work. Both lunges and step-ups have been shown to be more effective at activating the outer quad as opposed to squats. Therefore, unilateral movements can be incredibly useful for bodybuilders trying to bring up their quad sweep.
▪️ Source: Ebben, W. P., Feldmann, C. R., Dayne, A., Mitsche, D., Alexander, P., & Knetzger, K. J. (2009). Muscle activation during lower body resistance training. International Journal of Sports Medicine, 30(01), 1-8.