The low token velocity caused by steem being vested for at least 13 weeks at a time definitely helps support coin price. It slows down the rate of people earning it selling it. I think we've seen a lot of downward price pressure caused by Steemit Inc. dumping huge amounts every month to cover operating expenses, so that may be hiding how well that function would otherwise work. It's possible that there is no amount of "slowing" the pace of sales that can overcome the downward price pressure of people supporting themselves by selling earned coin (whether earned as a witness or content creator/curator). I hope otherwise, of course!