He doesn't use Twitter because he can't rattle on and on for paragraphs saying what he could say in 140 chars or much less.
I didn't have time to write a short letter, so I wrote a long one instead.
Different things require different amounts of space to adequately explore, and there are different depths you can go to for different audiences. This post was rather long, but I agree that 140 characters is generally too short.
As an example, just look at the abuses of language that occur so that people can fit everything into their 140 character limit.
"I have only made this letter longer because I have not had the time to make it shorter."
Blaise Pascal, (1623-1662) Lettres provinciales.
Not that the story need be long, but it will take a long while to make it short.
Henry David Thoreau
If I had more time, I would have written a shorter letter.
Marcus T. Cicero
You know that I write slowly. This is chiefly because I am never satisfied until I have said as much as possible in a few words, and writing briefly takes far more time than writing at length.
Karl Friedrich Gauss (1777-1855)
It is my ambition to say in ten sentences what others say in a whole book.
Nietzsche
The more you say, the less people remember. The fewer the words, the greater the profit.
Felelon
In this case, for once, we have a definitive source: Letter XVI of Pascal's Provincial Letters:
The present letter is a very long one, simply because I had no leisure to make it shorter.
http://oregonstate.edu/instruct/phl302/texts/pascal/letters-...
I haven't found any evidence that Mark Twain or Cicero said it. Especially in Twain's case, I suspect people just decided he said it because he's known to have been witty.
[Borges’s] sources are innumerable and unexpected. [He] has read everything, and especially what nobody reads any more: the Cabalists, the Alexandrine Greeks, medieval philosophers. His erudition is not profound - he asks of it only flashes of lightning and ideas - but it is vast. For example, Pascal wrote: ‘Nature is an infinite sphere whose centre is everywhere, whose circumference is nowhere.’ Borges sets out to hunt down this metaphor through the centuries. He finds it in Giordano Bruno (1584): ‘We can assert with certainty that the universe is all centre, or that the centre of the universe is everywhere and its circumference nowhere.’ But Giordano Bruno had been able to read in a twelfth-century French theologian, Alain de Lille, a formulation borrowed from the Corpus Hermeticum (third century): ‘God is an intelligible sphere whose centre is everywhere and whose circumference is nowhere.’”
This comment was much longer before I clicked "reply".