That, and you just didn't just go to a system that's hard to attack, but also hard to develop for. Can you write software for that microcontroller in C? Sure,

That, and you just didn't just go to a system that's hard to attack, but also hard to develop for. Can you write software for that microcontroller in C? Sure, although you'd probably prefer Rust. Now if you managed to find someone with a low salary who'd put up with writing screen software for a train, try telling them there's not just no Java, but no Heap and that they'd have to connect to the GPS chip via serial instead of having OS managed location. And then they'd have to integrate the streaming MP4 video for the advertisements on their own, without a filesystem or FFMPEG. Haha, not gonna fly. No product manager in their right mind would greenlight that effort for "security reasons" if it suddenly takes 100x the amount of effort then. We're using operation systems for the features they provide and the ease of development (as well as debugging) they enable, that's the answer.