BLE doesn't use pairing and Bluetooth isn't a "network" that devices need to join.
With bluetooth you don't have to discover a network, join it, and provide one of several login credentials, none of which many bluetooth devices have an adequate UI to implement. Joining a WiFi network during setup of smaller devices is a horrendous, unacceptable process. The equivalent process with bluetooth is either nonexistent (BLE) or a joy in comparison. Often time, even when pairing is needed, the process is entirely automatic. That can NEVER happen with WiFi.
Zigbee is a far better competitor to Bluetooth than WiFi is.