There is no clear reason why Google prohibits the recording of calls for applications from Google Play. In many jurisdictions, the consent of one or more participants is required to begin recording, but once the user fulfills this requirement, the recording becomes perfectly legal and useful. In particular, the Google Recorder application is a voice recorder for recording conversations that have similar requirements.
Google itself doesn't seem to have a problem recording calls when it comes to its own applications, for example, Google Phone on Pixel phones supports call recording in some countries. Google simply does not provide the proper APIs to allow third-party application developers to compete with it in this market, and is now ceasing to use workarounds.