I suppose it's a matter of acceptable approximations and cost. If only 2% of players have a high quality surround sound system, and only half of those have a good ear, then you really only have 1% of users who can tell the difference between raytraced audio and the heuristic "hacks" that sound engineers have spent decades developing. So I don't know if audio raytracing will become mainstream in games anytime soon. But I also suppose that if one engine does it, others will follow suit.
Same thing with this Unreal 5 demo. Most users would not be able to tell the difference between rendering 16B vs 8B triangles per frame.
You don't need a high quality sound system or a good ear to tell the difference though. You just need a pair of headphones and to be a human with hearing. Evolution has been at work for eons. Every human born is a powerful audio processing machine. I can't give you a rigorous proof or hand you a double blind test to try for yourself, so you'll have to accept an impasse or start going down a rabbit hole consisting of studies on pre-baked ray-traced FIR filters of known geometries and the audibility of group delay.
I am convinced every human can hear the difference. Computation is cheap. There's no reason not to solve the problem.
Forget all of the little hacks. Sound processing is cheap. In 2020 it is unnecessary to select from a set of pre-baked filters and applying them to some predefined volume (ie this room is echoey, this room is absorbant, etc.)
This is one area where software has regressed then stagnated [0]. It doesn't make any sense, other than it wasn't prioritized. I think it's only a matter of time before engines go back and finally complete the audio simulation problem.
0. https://www.youtube.com/watch?v=cS_Fbueh7F4