It actually worked this way in Windows XP. But the cost was too prohibitive and a design change in Vista disabled this approach. Explained well in this blog post, I'll quote the essential part:
In Windows Vista, the memory manager folks recognized that these long delays made very large pages less attractive for applications, so they changed the behavior so requests for very large pages from applications went through the "easy parts" of looking for contiguous physical memory, but gave up before the memory manager went into desperation mode, preferring instead just to fail.