Can someone explain why Enterprise Environment Factor is the input of Communication Project Management Plan?

To piggyback off of what Liana said, here is an example. In my company, we have meeting guidelines part of our organizational culture. Meetings begin on time and finish five minutes before the hour/half hour. A meeting scheduled from 1:00-1:30 would begin promptly at 1:00 and end at 1:25. This allows time for participants to go from one meeting to the next without being late. If I am managing a project that includes external stakeholders, that is an Enterprise Environmental Factor that I'd want them to be aware of, in my Communication Plan.