A fun demonstration of getting comprehensible sound via one bit sampling is that you can use a tight loop on a C64 to read from any number of input pins (such as the tape input) to sample sound, and play it back either by writing to any number of outputs and connect it to a speaker, or indirectly by using the signal to toggle the sound chip volume up and down.
So not only can you get comprehensible voices from a 5V I/O pin to a speaker, pretty much any CPU newer than the mid 70's will be powerful enough to drive it.
So I agree - there's not really any excuse other than that people haven't thought about the UI.
Careful not to burn anything out... Though the C64 is pretty indestructible - I connected all kinds of things to the IO lines of it back in the day... And a few inadvisable cases of soldering things straight to the user port pins (I'm amazed I never destroyed any machines.... that way)
A tip is to turn off the screen during sampling and playback, as otherwise the video chip steals a lot of memory cycles.
You might then also be interested in this far more impressive playback with the C64:
So not only can you get comprehensible voices from a 5V I/O pin to a speaker, pretty much any CPU newer than the mid 70's will be powerful enough to drive it.
So I agree - there's not really any excuse other than that people haven't thought about the UI.