It feels like no matter how many times I repeat a message there is always somebody telling me this was new information. It's hard to get everybody on the same page on any organization or group of people with more than a few members.
Repeating the message is one way. But it leads to a situation where growing number of people is just getting tired of hearing the same information over and over again. This leads to them not listening to you anymore. Even if you have new information to share! They just join the group of uninformed and the repetition cycle begins.
Anything but the smallest organizations also have a lot of information to share. It might seem that once you get the people listening it's better to tell them all the things at once. The problem is people are bad at digesting large amounts of information at once. So they will only remember the highlights from the topics that matter to them. The rest is as if they had never heard of it.
Writing down the information has a few benefits over spoken information sharing. It can be digested asynchronously, whenever the recipient has time. It's also easy to refer back to the text if something is forgotten. But there is no easy way to track whether people even bother to read all that info. It's also possible that people disregard the notifications of new bits of information and let them pile up to be read at later time. That leads back to the "too much information at once" problem. But at least they might have a faint memory of reading something and once coming across the topic there is always the text to check back.