We're crossing the threshold this year where real-time ray tracing in hardware isn't just some theoretical concept, it's actually useful and available in affordable consumer hardware (NVIDIA and AMD GPUs, as well as the PS5 and new Xbox all have it).
Yes, the NVIDIA 2xxx RTX series had it two years ago, but this is the year where it's actually viable and not so gimmicky.
It's also shipping in consoles this generation, which is going to drive a lot more games to actually implement it. When it's only being used by 5% of the PC userbase, maybe you don't bother doing that work. If cheaper GPUs can push that up to say 20% of PCs next year, you still might not.
But when every PS5 and XSX has raytracing hardware, suddenly it makes sense. That's going to be helpful for getting it supported in PC titles sooner.
We've been able to do realtime ray tracing in software since forever though and the shadertoys and whatnot have been full of hardware accelerated demos, that's not so interesting.
I remember playing with a number of demos on my intel core 2 duo macbook (not pro) a decade ago.
They weren't doing that in hardware real time accelerated at 4k resolution in AAA games. This year they are. That's a big leap from your core 2 duo demos.
The new GPUs have hardware specifically designed to do the type of math that raytracing does, such as ray/volume intersections, faster or more efficiently than generic shader hardware. Sufficient quantity (FLOPS) can become a quality of its own.
Yes, the NVIDIA 2xxx RTX series had it two years ago, but this is the year where it's actually viable and not so gimmicky.