And the number of RTL language (script) speakers in the world was dwarfed by the number of vertical script users in the world. Guess what? All those users are doing LTR horizontal text today (including Japan).
The change was largely voluntary. There's no need for Apple to do RTL support in order to penetrate those markets. Those users will get used to it or fall behind. Their choice given that the US, China and India all do LTR.
Urdu, Arabic, Hebrew script users will just have to cope with poor RTL support.
Arab World: 320M with a average growth rate of 2.3%
Pakistan: 173M pop, 1.99% growth rate
Iran: 65M pop, 0.79% growth rate
India: 1.1B pop, 1.58% growth rate
China: 1.3B pop, 0.62% growth rate
US: 300M pop, 0.88% growth rate
The growth rates may be higher but dwarfed by the huge head start of China and India and their largest pop base is not much larger than the US.
Let's not even talk about the relative economic power of those six countries/groups.