Some USB WiFi adapters need drivers because their internal chipset is not recognized by Windows. Each adapter uses a different chipset (like Realtek, Mediatek, or Broadcom), and if Windows doesn’t already include the driver for that chipset, you must install it manually.
“Driver-free” adapters work immediately because Windows already has built-in support for their chipset. When you plug them in, the system automatically detects the device and installs the correct driver without needing a download or CD.