| Looks like nobody else wants to, so I'll take a stab.
It's no surprise that rosewood is much less dense than ebony, and thus makes a fingerboard which wears out quicker.
In the guitar-world, my luthier pals take as fact that Brazilian rosewood is harder than Indian rosewood. It's safe to say that nobody's put Brazilian rosewood on a new DB fingerboard since around 1969. Plus, the lower (read: cheaper) grades may well be pulpier, softer wood, too. And these days, many factories aren't even using Indian rosewood, they use "rose-woid" alternatives, many of which are even softer.
That's probably most of the explanation of how a forty-year-old Kay can still be chugging along on a rosewood FB when a five-year-old Englehart is already toasted.
Incidentally (if you're still awake), my git-box pals say as a rule of thumb that a Brazillian board will take three or even four careful refrets, but an Indian board will not handle more than one or two. YMMV, but it's illustrative of the point. | 
