there is a lot that go's with OBDII auto company's dont have a choice.
The EPA has alot to do with the OBDII. Starting in 96 or 97 it was required by the goverment with a set of standards, including the connector, it's location and what code's auto makers had to make available with out the factory scan tool you dont have to worry about diffrent cables or connectors with obdII systems.
Any Generic OBDII scanner will pull codes, it just depends now how much futher you want to go, as far as getting FF data, watching PID's, recording data for live playback, testing systems.
Zach