We know that for firefox , driverserver.exe is not required while it is required for chrome or IE. Please help me to understand why Firefox is default Implementation of WebDriver.
From here - https://code.google.com/p/selenium/wiki/FirefoxDriver : Firefox Driver
Firefox driver is included in the selenium-server-stanalone.jar available in the downloads. The driver comes in the form of an xpi (firefox extension) which is added to the firefox profile when you start a new instance of FirefoxDriver.
Firefox is baked in the jar file. It comes as a xpi, which is the extension of firefox . As soon as you instantiate the FrefoxDriver it gets added. See this