It's a cheaper safer option to get something that looks "right". It's not so trivial to have 120 fps video look like a smoother 24 fps. Even capturing at 1/120 shutter speed it does look different. There's an experiment I want to do that involves taking 120 1/120 video and stacking windows of 3 frames to emulate shooting at 120 fps with 1/40 shutter speed.