Especially when accounts could be hacked to say anything, like the incidents a couple years ago. Imagine the POTUS account pissing off an unstable dictator in some country, or posting of some sensitive information.
When has it been any different? Before twitter, it was TV and radio. Before RV and radio, it was newspapers. All of these are commercial entities (with a few non-profit exceptions).
television and radio were at least publicly available and based on published/known standards. you didn't need to ask anyone permission to receive signals.
On top of that the FCC governs the airwaves and (at least in theory) works to ensure they meet public need. There are also other rules such as the Equal Time Rule. Twitter is subject to nothing like these things.
