The reason for different developers is not the photographer's taste, but their specific effect on different films' tone and grain.
D-76 produces an appropriate curve on contrasty Tri-X, while HC-110 makes soft HP5+ more vibrant... TMaxDev gives more speed and pushability for TMax for films, while Xtol and PyroHD are bought by people who consider less grain means better photographs.
What I mean is developers have real differences, and it's not true we can use any developer to shape a film's curve as if it was developed in any other developer: sometimes it can be done to a certain degree, but not always.
That's why several developers and different types of developers survive.
IMO we need a few: one for sharp grain and acutance, one for grain control in portraiture, one for upswept curves, one for pushing when there's no better option...
I have not found any developer that's the best option for all films and types of scene.