We don't! Instead, we go to regulators. Though I suspect your question really is "Why bother with salvaging Android at all?"
Mobile platforms are hard - famously, Microsoft failed to make Windows phone a viable platform, and John Carmack successfully argued that Meta didn't need a custom OS. Mozilla's Mobile OS that had OEM partners making real phones spluttered out, and nor for the lack of trying. Both Firefox OS and Postmarket rely on an Android foundation for HAL/drivers, IIRC. Device bring-up is hard, and negotiating with OEMs is harder still, and that comes "free" with Android-supporting devices.
Logistically, the vast majority of people who install apps from non-Play-Store sources do so ok their daily-driver phone, which is running the stock operating system. They are not tech savvy at all