People do that all the time though, often to disastrous effect. Once it stops happening IRL we'll stop making art about it*.
* while it does happen all the time IRL, I think some writers use it as a shortcut to get to the plot they want to pursue without going through the character development that establishes why a character might act this way. That is lazy and annoying writing, but it doesn't invalidate the whole trope. People really are like that. Clear communication is hard work and a lot of people just don't do it a lot of the time.