If vertical integration is a good business platform and one that creates and keeps jobs in the US, why is it not used more?

As much as people want to slam American Apparel they were a good example on how Vertically Integrated Company can work, not only creating jobs, making workers feel important, but keeping jobs in the US. Why is the system not used by more businesses? Aside from American Apparel, Apple is about as close to vertically integrated as I can figure (though there may be more out there unknown). Does it only work in select businesses and that is why it is not used more, or it isn’t because of unions, greed at the top, or foreign labor is just too tough to beat, etc.?