Between our own writing and teaching others about writing, these little marks and techniques take up a lot of our time. We often cover very technical topics from cell apoptosis to financial derivatives. Sometimes we need to use long sentences to convey the information. Without a good grasp of conventions, particularly punctuation, our hard work would be lost on most people. But a long, well-punctuated sentence, is both readable and understandable.
Learning this stuff could be a nightmare. I remember learning it the hard way back in grade school. Filling in worksheets, "correcting" incorrect sentences. Bleh! Nobody at school ever bothered to connect what I was learning to what I was reading and writing. Somehow, most of us figure that out on our own. But not enough of us do. Just ask the UNC J-School.
Most of us professional writers know the best way to learn something like this is to have to use it in our own work. I can't tell you how many style guides our little company has to use -- one for this client, another for that one and good ol' AP Style for the paper. We've learned each client's conventions, etc., by using them!
I wish more schools would use that approach. We bring this approach to our corporate training programs. If you need to improve your team's fundamentals, give us a shout. We'd be glad to talk more about our unconventional approach to conventions.