You'll notice similar trends in other "Americanized" martial arts diciplins.
Typically "Americanized" systems will have
10 Belts...Black ... 5 Ranks of Black
Whereas more traditional systems will have.
5 Belts...Black ... 10 Ranks of Black
This makes comparing belt colors kind of usless between systems (individual teachers are very different in some systems making them even harder to compare)
Many Dojo's treat Martial Arts as a business, and they realize that
-People like things where they are more frequently rewarded
-Kids are your big profit center
and adapt their training methods to suit.