ADRC Technology, page-43

You have to remember that the basis of IoT is low power communication - 6LowPAN compliant protocols. Phones don't use this, the mobile device communicates with the 'thing' by use of NFC, and then with the hub via wifi. The hub then communicates with the 'thing' via low power protocol.

The hub also manages the security side of the low power network, and I don't think that could be done from a mobile device which may or may not be in range. It is also the central database for all the 'things' on it's network.

You will always have wifi at home, so that you can create a LAN for devices to communicate with each other. If everything just worked on 4G or 5G or whatever may come, you would make your IP happy with the amount of bandwidth you would need .... and they make enough money as it is!

Be aware that computers and mobile devices are not IoT devices, they are active computing equipment, and in most cases only provide access to the apps to run 'things'. ADRC is different, because of the unique use of NFC to do the handshaking.