Hell, why don't they just add a DP to VGA adapter right in the box of the Video card? They've been throwing in DVI to VGA for years. If they want DP to become the new standard it only makes sense.
Because $35 is still $35. IMHO, it's more important for them to publicize viable alternative than to add cost to the default bundle of every 5000-series card. The trick here is product placement in stores with these adapters sitting right next to the cards on the shelves. The issue here is that is pretty much a store marketing promotion and AMD needs to see that it would help them with adoption of the tech if they promoted the concept of product shelf placement with adapters near by or bundle deals. That is probably outside the scope of their regular marketing campaign tactics though, as I don't think they would normally collaborate on that level with the retail chains. It's still beyond me why we don't see ATI certifying some OEMs, slap their EyeFinity certified logo on the product packaging and do a marketing promotion for EyeFinity compatible products.
Ultimately, all of us here are knowledgable thanks to community experimentation and research, but the unimformed regular target customer would have to dig really deep to gain this type of insight and most likely would not realize there was a bit of issue until they encounter it the hard way.