[potato3732842]

You can infer the same information it would get you via boost and EGT and whether or not your exhaust visually indicates unburnt fuel. You also don't need super precise AFR in a diesel like you do a high strung turbo gas engine.

Wide band O2 sensors are unreliably enough that they're kind of a pain to keep working accurately long term if you're not on a racecar maintenance schedule and if you aren't tuning things to those extremes you don't need that level of precision anyway.

Basically it just kinda adds up to "not worth it" for street vehicles