A number of the brokers don't allow scalping because they have their own type of the trading strategy. So, It depends upon the brokers policy that how it maintains it profit and loss ratio. A broker never want to get loss whether its traders are winning or not. He'll try to get maximum profit out of the market as every trader wants. So, Some brokers also use unfair means to get profit and they deduct the profit from the trader's trade which is really not a good thing for the traders.