In short, nothing.   Flame front ignition has been around for decades and functions well at many locations around the world.   Installed and used correctly FFG ignition systems function very well.  In many respects a simple flame front generator system is more robust than an electronic ignition system . which can suffer from burnt out ignition cables.   Provided that the the flame front generator is regularly used and maintained, it will provide many years of service.  The more recent preference for electronic ignitions is mainly due that the fact that they are easier to automate, require little operator training and can be initiated by the push of a button.