Tweets provide a lot of efficiency. "Tweets aren't great because the compress otherwise complex ideas". A decent summary of your essay and tweet-able. Point made in 5 seconds of reading. Yes you don't get the full emersion but thats exactly why both mediums still exist. The tweet saves time and consequently gets a wider audience.
It often takes multiple restatements of an argument to get it to sink in, because different readers are affected differently by any given set of words.
It often takes an essay (or a book, or a series of books, or a body of literature) to fully map out the consequences of what initially seems simple.
It can be difficult to truly impress the emotional texture of a concept in 140 characters without relying on cheap appeals -- which obscure the actual concept.
Here's the tweetable problem with trying to convey deep concepts on twitter:
