I can see how you could reason in that general direction, but I disagree. It's just my opinion, but I feel the goal of chat is to try to simulate conversation via text. So it tends to consist of a lot of very short "posts".
The people who hate, loath, revile, and just generally get ticked off about the Discourse 20 character post minimum are the same people who … just my opinion/guess … are likely to enjoy chat. Two words: culture clash.