Excellent question! I have no idea why it's set like that. The 6.0.4 release (due out by the end of this week) will have it properly default to "Global".
As for "all our modules", the only modules that this will be updated in are the SCSocialWidget and JFBCSocialShare modules as those are the only two modules included with JFBConnect anymore. All other JFBCxyz modules have been discontinued. The SCLogin module is included, but already has the global value defaulted properly.
I hope that helps, and thanks for pointing it out,
Alex
Modules set to "use global" by default please
