It's not that easy. If we look at how splintered the market in its entirety is, one entity or a group of entities will need to extremely overpay for their coins in order to own even a semi large chunk of coins in the end. Another thing is that banks or other wealthy entities don't trust exchanges and will not participate in them; their only way is to accumulate coins through private deals, which is getting increasingly harder with so much OTC demand.

Miners have plenty of buyers to sell their coins to, mostly at 25-50% market premiums due to their virginity. Services connecting OTC traders have to deal with far more demand (ie, more buyers than liquidity providers). People holding Bitcoin don't really want to sell many coins anymore with how the price will be going up. It's not easy to obtain Bitcoin anymore, especially not in extremely large numbers.