I don't think it's much worse than having an icon of mobile phone from 90s with a grid of buttons and external antenna. Almost no one is using those either. And a featureless rectangle with rounded corners in the shape of modern smartphone doesn't make a good icon. The best you can do is rectangle with circle for pre iphone X style home button or more generic slots for speaker/microphone which still makes a bad icon and are going away.

Having an icon of smartphone in a smartphone for the call app wouldn't be very helpful. And considering modern usage a smartphone doesn't even a have a strong association with calling.