The idea is not to count on a wire.
What if there is a clog (e.g. from a failed hose liner) or a crimped hose and brake pressure doesn't release when it is supposed to? It used to be the job of the man in the caboose to know that. Now it's FRED's. It's also his job to detect over pressure or failing pressure that will stop the train at a potentially inconvenient time if not addressed.
It would be nice to have both a wire and a wireless connection, but one of the ideas was clearly to avoid needing another connection between cars.