Many people these days over-notate their music. I propose three theories for this.
The first is that most people do not spend a lot of time working with a live orchestra so they do not have a lot of ‘match practice’. When they do get their time with the players, they want to make sure they have everything spelled out, and so they often overdo it. Thinking they are doing the right thing, they clarify things that do not need clarifying and state things that are either obvious to the players or an inevitable result of the notation or physics of the instrument. Inexperienced orchestrators do not know where and when the orchestra can be left to do its thing, for example the natural crescendos and diminuendos into and out of phrases. I have seen scores where the only other possible detail an orchestrator could add would be the note names themselves.
My second theory is that this excess notation is the fault of our software. In order for the playback to sound half decent it needs much more information than a human does. So people put a dynamic in every bar followed by a hairpin and an articulation on every note. Look at some old scores; there are not that many markings. Of course we do need some indication of how to play, but the art of orchestration is in finding the balance between what is needed and what is not; in short, knowing what the is and when you can rely on it and when you can not. To get a good idea of what is needed and how to notate your scores, it can be helpful to think about how you would write the score by hand if you were in a hurry. For example, with pencil and paper, you would only write staccato articulations once or twice for a repeated pattern, and then you would write simile (or sim. for short, as I prefer; means the same, and uses less space and less toner). But now people swipe a section and apply the articulation to the whole thing, or copy and paste a swath of markings, creating lots of redundant information.
Thirdly, some people think it looks ‘academic’ to have a lot of information on the page. An articulation on every note, micro-managed dynamics, and a text description on every phrase make it look like you have put a lot of work and effort into your score. The hope, I assume, is that a detailed score might appear more professional and get a better performance. In reality, you are cluttering the page, wasting toner, and distracting the players from doing their thing.
So what happens with all this extra information?
The orchestra is very forgiving and flattering. You can put just about anything in front of them and the players will make sense of it. You can over- or under-notate, go out of range or forget that people need to breathe and nothing bad will happen. Like magic, it gets sorted out. This is both good and bad. Good in that the players make it work, but bad in that unless you ask, the best players will not tell you what they have done to make it work. You will never know that they divided that double stop, split a line up between two people, or did not need to be told to ‘breathe when needed’ on a whole page of unbroken quavers (there is really no choice). It is not their job to school us; they play and take pride in making it work. In order to learn what’s going on, you have to be proactive and ask your players. It is very easy to go through life doing redundant or incorrect things and never realizing the fact.
Finally, one very practical reason for trusting the default and keeping the notation clean and simple is that in the studio things get changed all the time. Composers or directors often want to try things in different ways once they hear it live, or perhaps a picture change means things need to be tweaked. The less notation there is to change, the faster and cleaner it can be done.
When I mention these concepts, I often get the defensive response, ‘I just want to avoid any questions’. If you learn more about the default, you find that in many cases there can be no question. You just have to think before you ink.