If someone were to make a purchase on a coin exchange and bring it here it would be great for Steem's growth, but the problem here is that people who want to cheat the system like you said, they put back the amount of Steem they received here, and do Power- Up, then they made a post informing others that they had bought Steem on a coin exchange. That's something that must be considered at this time, so that there is no cheating, and there is no influence on the growth of Steem in the future.