I suspect a lot of people on this forum aren't old enough to remember
but there was a time when cars came, not with wimpy little donut "spare tires" but real, actual tires that were just like the ones that came on the four working wheels. But, that started to change sometime in the '80s I beleive.
It took people a while to get used to the idea but real spare tires eventually became something you only see now on cars in museums.
A similar thing is not happening with the donut spare tires being replaced by "repair kits". The kits save both weight and money...I don't know which manufacturer did it first or exactly when but I am pretty certain that Ford has been doing this since at least its '08 models.
What seems to have happened with the 370Z Roadster is that the demand for a spare tire rather than a kit far outstripped what was anticipated (I guess it's going to take a while for people to get comfortable with the idea). On top of that, the State of Maryland is the only state that REQUIRES a spare time in a car hence, every roadster that had an actual spare tire got slated to Maryland.
As I've said before, I haven't actually had a flat in years and even if I had a spare, I'd probably just call AAA and ask for a flatbed to tow me so I could get it fixed (of course as I say this, this will probably be the year i DO have flat!).