The real crux of why Arduino isn't EE-SE is because Arduino (and chipKIT, Raspberry PI, Netduino) as a concept are bringing novices into the discipline of embedded design. Many people exploring this new genre of embedded devices are coders. And not necessarily software engineers or programmers.
So to take the above and put in terms more people might relate to: it's like someone whose only "programming" experience is styling mySpace going onto Stack Overflow and asking about php for WordPress.
I have a BSEE cum laude with distinction in my degree, so I can appreciate how painfully newb some of the Arduino questions are on EE-SE. I'd suggest that once a QA on Arduino.SE was beyond the scope of the community's electronics experience, the question could be migrated to EE for better attention "worthy" of the EE-SE's time.
In no way am I looking down at the Arduino questions as I'm not equipped to answer some of the really EE based questions. My degree was focused on embedded programming, not fundamentals of EE design. :D