If Bitcoin price pumps from $1300 to $3000 in few hours, nobody would make profit from it, because the exchanges wouldn't allow you to sell your Bitcoins and make the fast profit, it would bring a big loss for exchange sites.
Do you agree with this?
Reputation is one of the important things for service providers such as these exchanges. If an exchange declines its customer in selling his assets then that would definitely ruin the reputation of the exchange. And surely, that is not good for them. Instead of having profits, the might end up without customers at all.