Reverb has sort of been a thing for a long time, albeit at varying degrees of quality. Aureal was actually playing around with both directly-geometry-aware reverb and binaural audio w/ HRTFs way back in the 90s, but they sort of got murdered by litigation shenanigans from Creative Labs. Reverb based on per-area filters has seen plenty of implementation over the years, including being used very strikingly in Halo.

Recently some games have tried more geometry-aware reverb. Killzone Shadowfall is a notable example, although overall the audio seems kind of muddy.

I wonder if part of the issue is audio HDR. I have no idea what sort of ranges games tend to store audio samples with, but I'd think you'd want the source file range to be WAAAAAAY wider than the output range if you wanted to produce natural reverb. Just like how you need the early stages of a graphical pipeline to have incredibly high luminance range if you want post-process effects like bloom and motion blur to be accurately captured from the underlying scene. (For instance, Halo 3's backbuffer can store pixels that are up to ~128 times brighter than the maximum output levels.)