Simply put, it’s because we don’t know when the bridge will reopen. Once ice begins falling from the towers or cables, shaken loose though higher winds or rising temperatures, it’s impossible to know when that will end. Sometimes closures end because the ice has melted and completely cleared; sometimes it’s because temperatures have dropped and the ice freezes back into place. We can and do look at weather forecasts and our own atmospheric equipment so we can alert our Twitter followers that conditions are likely to result in falling ice, as well as during closures to see when winds or temperatures are likely to fall (or rise), but the ice has a mind of its own and leaves at its own speed.
Please refrain from calling the Authority office for updates during a closure; until the bridge reopens, there will be no different information available.