I'm sorry if this isn't an appropriate place to ask this.
I taught a couple years in a secondary school, where teachers are supposed to explain every little step in the simplest but accurate way.
In high school things don't change much. Perhaps the pace is a little faster but still the goal is to be as clear as possible. Teachers are supposed to use pictures, animations and justify every step when solving problems.
In the university things are a lot different. We get exercises every week and solutions are extremely compact. I don't mean to show every little step when computing a determinant of a $3\times 3$ matrix but often one reads "one implication is trivial, one can (easily) see that, it is clear that..." and so on, which makes me personally feel incompetent because most of the times I don't easily see what I'm supposed to. At least in secondary school, it is mandatory to avoid using words such as "trivial, easy" and so on because of that reason. Still, some teachers do it and some believe this to be one of the causes of the spread of anxiety for mathematics, which certainly hinders the learning process even more.
This applies to this platform as well. The style completely changes. Why is that so? Are compact solutions more elegant? Are mathematicians just lazy?
I'm very curious about it.