I believe DMC1 didn't have extra content, that was DMC3 (but I won't swear to it). I do know that there were regional diffs in difficulty level from JP to NA for the original release of DMC1.
Bonus content in the GH titles has been up to the individual publishers (like Capcom and Konami), and has been more the exception rather than the rule. In the past gen, it often resulted from the diff release schedules between country as well as platforms, and the discovery that customers actually would rebuy a title if it had new content. So if a title got tweaked for a Region 3 release, the release sold well, and there seemed to be NA demand with a GH release, why not take advantage of it.
It puts out a lot of SKUs, like for Call of Duty 2 (standard, SE, GHSE), but more SKUs means broader distribution, higher quantities in the various sales channels.