The flip side of this is that attention spent on writing is attention not spent on understanding what you're seeing/hearing. Back in university I had a professor whose English was sufficiently messed up, combined with the fact that lot of what he said was simply wrong, that I couldn't understand him in realtime. By the time I figured out one sentence I had missed enough of the next I wasn't going to understand it.

Fortunately, all I actually needed to do in class is to figure out what he got wrong so I could give the "correct" answers on tests.

(To illustrate how far out of it he was--this was a 400 level class. The first class period someone he had confused asked a question that anyone who had met the prerequisites should trivially be able to answer. Instead, he rambled back to what he had been saying. Repeat. The third time someone else answered.)