[1] https://en.wikipedia.org/wiki/Telephone_call_recording_laws#...
[2] File to edit: https://github.com/LineageOS/android_packages_apps_Dialer/bl...
Maybe it's complicated for telephone conversations where you're not breaking a law locally, but are breaking a law remotely?
Android doesn't expose it because the hardware doesn't expose it to the OS in the first place.
Well... IIRC there was never an official call recording API, and in fact on some phones it was physically impossible to snoop on the telephony audio.
Most recording apps used to either work only on some qualcomm single chip phones where baseband exposed audio path to application processor, or enabled microphone recording in hopes of catching the audio from speakers (and not all phones allowed simultaneous mic use like that).