If someone shares an opinion with you, more likely than not, they're looking for confirmation that you agree with them. Or that you think they're smart. Or, at the very least, they're asking you to hear them out and acknowledge that you've at least considered their point of view.
You can read any number of "How to Make Other People Like You" type books, and most of them are elaborating on that basic idea: when people talk, validate them. (This is not to reduce the content of these books, but that seems to be the essence.)
This is why social media, like Facebook and Twitter, works so well: validation is quick and easy. You can post something quick and short to a receptive audience, and people validate you by clicking the "Like" button, commenting, retweeting, and so on.
This explains why the world is growing more "chunky". A sentence is better than a long, multi-paragraph version of your own opinion, because if you post something short, more people will consume it, and this proportionally increases the number of "validation hits" you're going to receive.
If you write a research paper, there's a chance that only a small handful of people will ever read it, and those that do might all hate it. If you write a novel as a new or obscure author, it's the same dilemma: small potential audience, and the chances that anyone is going to validate your work is next to zero.
This is why word processors sit open and empty with people staring at them, while they're thinking, in the backs of their minds, "I wonder what's happening on Facebook?"
This is why students in classrooms are more attracted to what's happening on their smartphones than what the teacher is doing on the blackboard. Their phone connects them to all the people who like them and validate them. The teacher, in my experience, represents the antithesis of this: a menacing authority that could call on you to answer a question, and if you don't know the answer, you'll feel like a fool.
It should be easier for me to write a paper for a class and get quick validation on some pieces of it. It should be easier for me to work on a math problem and feel like someone is proud of me for having attempted the problem, even if I got it wrong and I have to start over.
Of course, I'm oversimplifying, and that makes the solution seem easy. It's not. But I firmly believe this: that sociotechnical systems have to evolve so that grander aspirations are easier for our peers to discover and validate for us. As human beings, when we do stuff and we're validated, we do more of that stuff. (Will the real B.F. Skinner please stand up?)
Here's the executive summary: if you want me to do it, make it clear to me that someone else gives a damn.
And in most cases, this is extremely difficult, because the world is desperately short on people willing to take the time to express how much they give a damn.