Regulatory Certification is also critical, you are not allowed to use home made RF devices, especially if they are connected to a network of certified devices.
For example the latest cellular standards use shared medium- everybody are transmitting on the same frequency at the same time, but you need to follow strict guidelines for power control and coding. One malfunctioning phone transmitting too strong can disturb a whole cell.
This is hard to achieve using an open source model since tests are conducted on finished products, whole assembled phones.