We are at a point in history where the electrical telegraph is well established.
But people don't want to press letters one by one on a switch. They want to talk!
The first phones appear to have used telegraph lines directly.
Also wired phones don't require modulation, which likely made their development much easier than wireless voice transmission. You just send the signal as a voltage differential directly obtained from the air pressure: how the telephone works.
Video 1.
Phone Intercom by Make (2014)
Source. This video illustrates will the incredible simplicity of the connection of a telephone system. Compare that to the relative complexity of wireless communication, which requires modulation.
Video 2.
Making a Microphone Work with an Oscilloscope by Environmental Radiation LLC (2012)
Source. Not the most detailed setup, but good.
ethw.org/Picturephone good article!
Video 1.
AT&T Picturephone Model 2
. 1969

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