It is somewhat baffling that most interactive, consumer-facing operating systems are not real-time. I suppose that it’s a product of legacy and technical debt.
Apple did announce that they’re using an RTOS in the Vision Pro. Maybe the VR/AR space will make this more common, since the latency requirements are more stringent.
RTOS are not going to become consumer operating systems, because there's too much value in selling it as a capability to enterprise customers (who are largely the consumers who REQUIRE a RTOS, rather than it merely being a convenience).