Everyone's got their own comfort level with respect to risk and cost, as well as intended usage.
Good thing there are multiple options on the market for the guy that just commutes to and from work, to the next guy who regularly submerges their bike in mud and snow, and nothing on the bike or handlebars is safe from damage.
Personally, there are a lot of important things on my phone. Not just contacts and calendar, but every kind of authenticator is now tied to this device and losing or wrecking my phone is like losing my wallet. So it stays in my pocket far away from harm.
Also, in the event that I get separated from my motorcycle in an unfortunate incident involving rocks, trees and cliff edges, then it's no problem pulling out the phone with the one arm that isn't broken to call for emergency services... and a winch...
Is a phone mount on the handlebars suitable for 90% of riders. I think so.
YMMV.
If you need access to the apps and services on your phone while riding, I like the idea of a proxy screen, like the Chigee or Carpuride, which mirrors the screen on your phone via Apple Carplay or Android Auto, and communicates to your phone in your pocket or luggage via Bluetooth.