[nevcairiel]

RTX cards come with Ray-Tracing hardware, GTX cards come without it. I really don't see how this is that confusing.

And for Ray-Tracing popularity, it just takes time to develop. Just this month it was announced that both UE4 and Unity are gaining Ray-Tracing capabilities, which should open the market for a lot more potential games supporting it in the future.
Combine that with a much larger hardware-base (ie. Pascal card owners), and it might be far more common in the future to have at least basic effects that maybe even Pascal owners can use, and once you have that, the jump to advanced effects is only a small one.