They did. Get an Apple Watch. Well, yeah... It does work, pretty well, and I figure, if no one couches, or licks my iPhone, I can touch the screen and get it to wake up with my Apple Watch. They have tried to address the issues. Heck, I ride bikes a lot, and can barely recognize people I ride with nearly everyday when I see them on the street (in the wild) without their 'stuff' on. Wiping down phone screens, using the Apple Watch, using hand sanitizer, not touching your face if you think it's unwise, will do much to lessen the possibilities, but seriously, it's not a gigantic issue. What are the chances of getting infected by touching your own iPhone if no one else ever touches it? I wouldn't think it's enough to get all flustered over. People have way more chance of getting infected standing next to an infected maskless person, touching anything and then your face/mouth, etc...
Think about it for a minute: If touching your screen to enter a passcode is so traumatic, touching the touchID spot has to be just as disastrous, right? Relax... Light switches, door handles, knobs, counters, etc, are a much more ready source of infection.
Someone said nitrile gloves were 'the answer' and then someone posted a picture of a guy handling his phone with his disposable glove in his mouth. Yikes, but there it is... Be safe, but be sane...