Don't blame the manufacturers, blame the government. For Ford/GM/Nissan/Mercedes to offer factory 4wd, they'd have to not only develop the parts but also crash test all the new vehicles, etc. Those extra expenses (according to their accountants) exceed the extra profits they could make.
A third party group like Quigley, since they're not the manufacturer, isn't as regulated to death. Also, a third party group can charge more than the manufacturer since they are willing to build a lot less per year to turn a profit. Look at what any third party group charges for a 4wd van - over $10k, compared to less than $4k for a new AWD Chevy van over its 2wd counterpart.
Naw, I'm not blaming anyone. The big 3 (6?) are full of smart people, and they're chasing a profit as they should. If there was a market for a factory 4x4 van, they'd build it. Its just frustrating that Nissan has what looks like a Titan based vehicle and they didn't put their 4wd system in it. Yet.
So how hard would it be to swap in the 4wd bits from a wrecked Titan and make it awesome? If it can be done, SMB could do it. Alan, what say you?