Don't know where this criticism comes from but temp and dewpoint data absolutely matter for air traffic, because it determines cloud bases. If cloud bases are below the decision height for the instrument approaches into an airport, it's illegal for a commercial operator to depart from there (because they could not reliably return to the field in case of emergency after takeoff).

The standard data output of an FAA weather station is in degrees Celsius, however, there is no accuracy more than that.