Flying around low in normal operations purely in case of a transmission failure is not sound thinking in my view. That's like not going outside just in case you get struck by lightning.
Do it when you have to for a valid reason, otherwise operate at a safe and sensible height. Less birds and wires, better radio comms, a bit more time to execute an emergency landing. Of all the emergencies one can have, it's only a very small percentage where a few more seconds before landing would have made a difference, and in the case of a main transmission failure you are most likely dead no matter what height you are at.
Risk vs Gain is one equation to manage well in aviation.