A motherboard typically provides one or two addressable RGB headers, and a build with six or more lit fans needs far more connections than that. A hub takes one header and fans it out to many devices, all showing the same synchronised effect.

Hubs also solve the second half of the problem, which is fan power. Combined hubs handle both PWM speed control and ARGB lighting from a single mounting point, replacing a tangle of individual runs to scattered motherboard headers with one tidy loom behind the tray.

Some hubs work purely as splitters under motherboard control, while others include their own controller with a physical button or remote for builds where the motherboard has no addressable header at all.