This may be a stupid question but why do we keep developing two different rule sets?
Would it be a crazy idea to fully merge the rules so we have one rule set again (let´s not talk about AUDL-Rules)?
As far as i know most players don´t care that much about the advantages/disadvantages of each rule-set. WFDF has just released a new version of their rules. There is little to no discussion about it. I guarantee if WFDF would have just said: We discontinue our own set of rules and from now on will play with the USAU-Version there wouldn´t be that much of an outcry.
Some people would be unhappy about the introduction of observers but apart of that I don´t see any USAU-Rule where the rest of the world would say: We can´t play with this.
There are other philosophical differences between the WFDF and USAU approach, some of which stems from the use of Observers, or around simplicity, or this key principle: "there are no harsh penalties for inadvertent breaches, but rather a method for resuming play in a manner which simulates what would most likely have occurred had there been no breach"
A more reasonable question could well be - why would a National Federation continue to have a rule set that varied from the rules of the World Federation?