AIUI, one of the worst cases of interoperability legacy I've ever seen. If even one thing in the pipeline is compatible with POTS ("plain old telephone service", i.e., land lines in all their 3KHz glory), the whole call degrades, and since the whole call is going to be degraded anyhow, almost everything written to handle voice calling just drops straight to the POTS lowest common denominator. Which in a digital world can be even lower than POTS due to our ability to just set a number on our lossy compression codecs with all the regard for how much money bandwidth costs and no regard for quality.
This includes hardware too, e.g., microphones that work fine in the POTS frequency regimes but don't produce high quality audio, speakers chosen just to work well in the old frequency regime, etc.
So, despite the fact I have to imagine the odds of a call hitting the actual physical POTS system approaches zero today, and that in general in 2023 a high-quality phone call wouldn't actually be that expensive, the odds of a call traversing something that lazily fell back to POTS-level standards for whatever reason is still quite high.
One could write a brief sci-fi story in a Star Trek-inspired universe in which galactic war is started because the video call to High Command in the year 2642 is still running on POTS audio quality standards and some words are fatally compromised....
To be fair to POTS, it at least made up for frequency response with near zero latency. What you describe is worst of both worlds -- latency of commodity packet switching plus bandwidth of POTS.
Personally, I'd always choose zero latency over audio fidelity in a two-way communication medium.
This includes hardware too, e.g., microphones that work fine in the POTS frequency regimes but don't produce high quality audio, speakers chosen just to work well in the old frequency regime, etc.
So, despite the fact I have to imagine the odds of a call hitting the actual physical POTS system approaches zero today, and that in general in 2023 a high-quality phone call wouldn't actually be that expensive, the odds of a call traversing something that lazily fell back to POTS-level standards for whatever reason is still quite high.
One could write a brief sci-fi story in a Star Trek-inspired universe in which galactic war is started because the video call to High Command in the year 2642 is still running on POTS audio quality standards and some words are fatally compromised....