The point is that if the A's decide that streaming rather than terrestrial radio is the future of play-by-play, they won't be taking the inconvenience of, at most, hundreds of people in the ballpark into consideration. Those people are already being reached by most of the A's advertisers through signage and between-innings ads on the video board. Play-by-play broadcasts are designed for people at work, in cars, at the beach, etc. They can't see the game, so it doesn't matter if the home run leaves the park 10 seconds before they hear the call.
With streaming the delay is measured in minutes. The San Jose Sharks broadcast the games on a transmitter in the arena. Why wouldn't the A's do something similar?