They do, but via wifi. which needs to be centrally controlled,...

They do, but via wifi. which needs to be centrally controlled, so if it is connected to a network your phone follows the protocols set by that network - timing, routing, IP addresses etc.

If there is no network, you can make your phone a hotspot, where it takes on the role of the wifi controller and issues the protocols for other connected devices to follow.

Phones are equipped with wifi and Bluetooth ... that is the extent of the radio output available. There is not much point in making them IoT compatible, as if they are absent, the network needs to find a new central controller to operate, and all the security and management would need to be rebuilt around that new controller.