I think Bibaculus hit the nail on the head. Most of the western tongues are Latin based, hence Latin influence must weigh heavily. It seemed rather simple to me when i was reading the posts. I believe the authors were writing for their audiences, in other words writing the way their audiences would readilly accept them.

As far as the Germans, or the forefathers rather, they were some of the biggest antagonists of the Romans, so maybe they didnt use the Roman forms out of principle.