Pentax's sudden infatuation with ED glass.

[David Oswald]

I'm curious.  In the days of 35mm SLR's, Pentax had a few ED lenses; 
mostly fairly long telephotos.

Now that DSLR's are the up-and-coming thing, suddenly we're seeing ED 
glass in the 16-45, 50-200 (as yet unreleased), and the 12-24 (newly 
announced).  AL elements have also become more commonplace.

So the question is, what's going on here?  I see a few possibilities:
* ED glass has suddenly become cheap enough to use in a broader range of 
lenses.
* ED glass has become necessary to produce acceptible results with DSLR's.
* ED glass has become enough of a recognized feature that using it pays 
dividends in improved lens sales.
* Pentax has become committed to producing better zooms than ever 
before, possibly to try to close the door on 3rd party lenses (much like 
SMC does).

Much as I love my Pentax equipment, I can't help but wonder if the 
sudden proliferation of ED glass in Pentax's DA lenses is because 
without the ED glass the lenses on DSLR's wouldn't live up to the 
performance of their FA equivilants in 35mm format.

The same question could apply to the proliferation of AL elements in 
recent lenses, though this trend actually began back around the late 
90's, so it's not as new of a trend.

I would love to hear that AL and ED elements common in recent Pentax 
lenses represent actual improvements to image quality, size, weight, 
and/or cost/value over lenses produced without these types of elements. 
 Is this actually the case?