Perfecting buoyancy control enhances all your diving, but especially benefits these activities:
Drift diving: Drift diving is all about floating with the current and enjoying the ride and it's a lot more fun when you're not constantly fiddling with your BCD.
Digital underwater photography and video: Nothing messes up a photo/video opportunity faster than kicking up the bottom, which is exactly what overweighted divers do. Perfect buoyancy = less silt. Less silt = better images.
Cave diving, technical wreck diving and other forms of tec diving: If you're interested in tec diving, make buoyancy control mastery a priority. When penetrating caves and wrecks, you rely on precise buoyancy control to keep from obscuring the visibility, which is kind of important if you want to find your way back out. You may have to hover for more than an hour at specific depths to complete decompression. And don't even think about doing these activities without the proper training and equipment. See your instructor about the DSAT TecRec courses.
Fish watching and observing nature: Nothing runs off critters more than flailing about. If your buoyancy's poor, the more you kick and scull to maintain depth. With perfect buoyancy control, it's like you belong there. You glide quietly and effortlessly, meaning you're less threatening to fish and creatures. So, you see more. And you can get closer to fragile organisms because you don't have to maintain as big a distance to keep from damaging them.