Right. You don’t have to do it but just like in filmmaking we have all these rules which are a film language that have been developed over 100 years and if you break them without knowing you’ve broken them the audience will be confused. There’s a lot of freedom within that structure though. Basically the entire history of cinema has been largely within it.
Discussion
This is probably because people in the industry over time noticed what worked and didn't work with people, and chose to respect it. In other words, they noticed the nature of the reality of people and how they receive information and submitted to it rather than trying to engage in some massive Pygmalion project.