system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Despite every other form of technology has improved rapidly, why has the sound quality of a telephone remained poor, even when someone calls on a radio station?
gpt
This gets asked often and you have a slight misconception. Telephone quality has remained the same, because what's called Plain Old Telephone Service (or POTS) *is* pretty much the same because it's ubiquitous and it works. 

But the technology that's used for what telephones are used for *has* improved - we have *other* technologies that far eclipse POTS and *are* available. ISDN, for example, has been available for decades - ISDN calls are so crystal-clear that many phone companies *add artificial noise* to the line because people were assuming the line was dead! But if you wanted ISDN, you had to pay a *lot* more, whereas POTS was already running to your apartment and mandated to be cheap! 

Nowadays you can also get phone services through your cable company, or use a cellphone, etc. Many people are switching away from POTS.