The host sets up a GATT server and the other players have a client role.
The other option was setting up a game via whatever WiFi network was available, but many hotspots now restrict peer to peer access. For cross platform support, iOS doesn't allow local hotspot creation (which could have been an alternative) even thought Android does. Bluetooth was the option that all platforms could support without having to deal with third party WiFi.
The host sets up a GATT server and the other players have a client role.
The other option was setting up a game via whatever WiFi network was available, but many hotspots now restrict peer to peer access. For cross platform support, iOS doesn't allow local hotspot creation (which could have been an alternative) even thought Android does. Bluetooth was the option that all platforms could support without having to deal with third party WiFi.