And there are two facts:
1. The number of people who have accumulated enough coins are increasing
2. The bitcoin price now is at a level that it can support some serious spending, 10 bitcoin can buy you a travel package
After someone have acquired hundreds and thousands of bitcoin, they might consider spend 5-10 coins to buy something, since this will not affect their total holding but still provide some usage
The problem is that currently there are still not a lot you can buy with bitcoin. In most of the cases you can only sell it and spend fiat, if there are lots of merchat accept bitcoin, for those people who want to spend the coins, they could just spend them, there will be no sell presure on the exchange