It's usually a product of two
It's usually a product of two things: manufacturing speed/availability and parts exclusivity. The first is a problem that Nissan should definitely not have, as they have one of the largest and most flexible manufacturing infrastructure in the world and no capacity stretch (unlike Toyota, who's in the near-opposite position). The second is something that happens because the vehicle is all-new and after-market makers are not yet around (often due to patents or other protections, but usually due to newness).