At least with the states I've seen, there are probably more similarities than differences. Or at least as many similarities as differences. Most states require something along the lines of, "APA-accredited or equivalent" for graduate and internship training and have similar grandfathering clauses, which is a start. After that, though, you're right--there are too many discrepancies. Postdoc year vs. no, oral exam vs. no, jurisprudence vs. no.
This likely reflects, in part, the significant variability in standards across training programs, and the desire for folks to not want themselves to be disqualified from licensure. What we have to realize is that if we're going to set standards, and if those standards are going to be adequate, we're going to upset some people. That's ok. It's why I make no apologies for supporting ABPP certification in neuropsychology as a universal standard, for example; if you don't meet those criteria (and have graduated within the past decade or so), I generally don't view you as an adequately-trained neuropsychologist.
I do see much more professional interest and activism in my classmates than I have from former well-entrenched supervisors, though, which is a good start.