If everybody will use only the trusted platforms it will be impossible for new platforms to develop because nobody will use them.
Are you willing to entrust your money to individuals you do not know? or trade in an untrustworthy location?
Traders require assurance of trade security at your platform. How can we trust you if you don't ensure trade security at your platform?
They changed their smart contract and do not pay. It is better not to trust the people that you do not know not to be desipointed and not to lose money.