Everything has a cost. Physical switches that are frequently used are among the first to fail. This is partly why iPhones got rid of the home button in lieu of Face ID. Now, macbooks automatically start up when the lid is opened - this saves an extra button press to the power button. Over the lifespan of the device this reduces wear and tear on common buttons significantly.
What would be nice is physical switches that are easily replaceable - but this also impacts a device's water-proofness and thinness. And the market prefers those two factors over switches, generally.
I see what you are saying. But a switch to turn off/on the microphone would not be used as frequently as a home button. This is why Apple still has the ring/silent switch on the iPhone. This was introduced with the first iPhone and still exists today.
There is a physical switch. It's the lid. It's not even a soft switch, the article clearly specifies that it's done in non-reprogrammable hardware logic, which is immune to tampering even by Apple who has bootloader signing keys.
That's a pretty poorly designed switch, if your intention is to turn off the microphone while otherwise using the system.
It's better than not having any way to disconnect the microphone, but strictly inferior to any system where you can toggle the desired state at any time.
