Over the last century there have been numerous improvements and innovations in fishing equipment, but spinning tackle still remains a staple in the sportfishing industry and for good reason. Conventional spinning gear offers several advantages over baitcasting gear, especially in the realm of light tackle fishing.
1) For starters, spinning tackle can throw lighter lures farther. From weightless baits to lures up to a 1/4 of an ounce, a spinning rod and reel is hard to beat for distance. Baitcaster enthusiasts may tout better "lure control" with heavier 1/2 - to 1-ounce lures, but when it comes to casting a lure weighing only 1/16th of an ounce, they'll be quietly reaching for a spinning combo. For this reason, spinning tackle has no match for casting 1/32-ounce Beetle Spins and jigs for panfish or light spinners for trout. In the saltwater flats, sailing a 1/8-ounce jig into a pothole at 90 feet is hard to do on a baitcaster. Even in the baitcaster dominated world of pro bass fishing, the top pros in the world still use spinning tackle regularly for shaky heads, drop-shotting and throwing light jerkbaits and crankbaits.
2) If wind is an issue at all, spinning tackle's advantage grows even greater. Backlashes bloom in baitcasters being cast into the wind. Casting across or into the wind is much more efficient with spinning tackle, especially if the lures are on the light side.
3) If you want to skip lures under low hanging cover such as docks, piers, bushes or the low limbs of cypress trees, then spinning tackle again outshines baitcasting gear. Yes, professional bass anglers who fish for a living are able to skip lures with baitcasters, but it takes hundreds of hours of practice to become backlash-free when skipping baitcasters. If you are looking to start skipping lures immediately, without practice and backlashes, spinning tackle is far more forgiving.
4) An often overlooked benefit of spinning tackle is it allows your lure to sink down straighter without as much "pendulum effect" from the rotational spool found on baitcasters. When a lure sinks from a baitcaster, it encounters resistance in the form of pulling the rotational spool, which causes a lure to pendulum towards the angler as it sinks. This is why anglers using baitcasters in deeper water will sometimes strip line off the spool by hand, to feed the sinking lure resistance-free line so it will free fall. Since the line on a spinning reel will uncoil freely from the fixed spool, it encounters far less resistance than the pull needed to keep a rotational spool moving. This is critical when fishing vertical cover such as pilings, standing timber, steep bluffs, seawalls, or tall vegetation in deep water. It's also key when targeting current breaks where you want the lure to fall straight down into the eddy.
5) Are you right-handed or left-handed? With spinning gear, it does not matter because on most spinning reels the reel handle is swappable between the right and left sides to fit your needs. With baitcasters, there are no swapping sides with reel handles; you either buy a dedicated right-hand model or a dedicated left-hand model and that's what you're stuck with.
6) One last big advantage of using a spinning reel is that you can easily adjust your drag during the fight with a fish. Whether the drag is on the front of the reel or the rear of the reel, spinning reel drags are often easily accessible and liberally graduated, giving you full-range adjustment during the battle. This is not to say that baitcasting reels can't be adjusted during the fight, it's just that the drag location is right next to the handle and trying to rotate it while fighting a fish is a little more complex.
Farther casts with light lures, more efficiency in the wind, easy skipping under low hanging cover, a straighter fall to the bottom, swappable reel handles, and an on-demand drag system that can be adjusted at anytime it's no wonder spinning tackle is still a standard in sportfishing today.