Most platform racing series were established by enthusiasts and then when the events started growing in size and becoming more popular (including significant media acknowledgement) is when most manufactures will step up to support.
All things considered Scion (Toyota North America) has done a pretty decent job at supporting and promoting various events, but their efforts are spread amongst everything from drifting to show queens and as with most companies they have a modest budget to spend and they are just trying to spend it everywhere rather than one target demographic.
Take other platforms like the Honda S2000 or the Acura NSX, I don't see too many dedicated sanction events for those platforms.
Most race teams are private teams, independently owned getting some support from the manufacturer as well as other sponsors.
Check out
www.Spec86.com and
https://www.facebook.com/groups/Spec86/
Mike is doing a great job of trying to establish a 86 platform series.
I own spec86.ca and spec86.club. I'm trying to do the same here on this side of the border, but it requires time, dedication and money - with a family and a full-time career its becoming difficult to do. However like all of us I have a passion for this platform and its a labour of love.