You forget that these are OTC markets (forex, cfd on futures, cfd on stocks).
That's why we can use our terms for trading.
All brokerage companies, dealing centers and so on, which offer OTC markets, earn money when YOU lose it. Because if you earn, THEY lose. That's why there is stop hunting, bad execution, bad quotes and so on.
Our company places difference between positions of our customers on primary markets. You earn, we earn. You lose, we lose. But we get commissions and part of spread.

Frankly speaking, i don't beleive in any interbank when we talk about forex. That's why for hedging forex we use currency futures on primary markets.

One more time: All the markets we offer, are OTC markets.