I see people are responding about performance considerations, but the other aspect is support. It may just be that NVIDIA does not believe supporting RTX Voice

I see people are responding about performance considerations, but the other aspect is support. It may just be that NVIDIA does not believe supporting RTX Voice on GTX cards is worth the time and resources. Because even if they put in a disclaimer about "We haven't tested this on every GTX card, so you may notice poor performance or bugs and we won't support that", they'll get plenty of people complaining to them about poor performance or bugs. It happens all the time, and it's often a big concern in choosing which products to support. Yes, I agree that initially choosing not to support GTX cards was a money-based decision, but sometimes there are additional (somewhat more reasonable) factors that contribute to that money-based decision, which people often seem to leave out.