Lots of ECN forex brokers offer the classic MetaTrader 4, better known as just MT4, as either their main trading platform, or as one of several trading trading platforms to choose from. For many independent traders, MT4 is already a familiar tool, which is also one of the main selling points of the platform. Not having to learn a new platform when switching between brokers saves valuable time and effort that should instead be spent on trading.
The MT4 platform was not originally developed with ECN trading in mind, but rather for dealing desk brokers who act as market makers for their clients. However, new innovations such as bridging software that creates a bridge between MT4 and the interbank forex market have made ECN trading on MT4 possible.