Why pre-dreadnoughts still used fighting tops

Why did early Royal Sovereign-era battleships retain fighting tops?

They still depended on visual observation, so elevated lookouts remained necessary without radar or other modern sensors.

Royal Sovereign-era ships had no radar or electronic substitute for human observation. The fleet still depended on the unaided eye to find threats and understand its surroundings. Height extended the visible horizon and improved the lookout's view over smoke, spray, and the ship's own structure. Fighting tops therefore remained practical sensor positions even as other elements of warship design changed.