That's because most "new" f/o's who show up for the right seat of an airbus or 747 have experience. They come from being captains or f/o's on other fixed wing a/c.
The candidates coming to an f/o seat in a two pilot helicopter may be brand new pilots ( 100-500 hr experience) or high time single engine/single pilot guys.
There is a HUGE difference in the CREW experience dynamic between fixed wing and helicopter.
DK