[BertoldVdb]

That functionality is absolutely non-trivial. There are a few WiFi cores (digital and RF) you can license but they are expensive and the analog part uses a lot of die area. If you look up die shots from the ESP chips, you see that the radio is more than half of the die.

Espressif apparently has their own WiFi implementation, which makes sense as they are a major vendor of very cheap tablet and cell phone WiFi radios. This is likely why they can offer that feature so cheaply.

Bluetooth Low Energy is way simpler BTW.