As long as you put your phone in a good protective case, which extends higher than the camera modules on your phone, I personally don't see the need to pay for lens protection. But, that also depends on how you treat the phone when not in your hands. If bouncing around in a backpack with other hard objects, then perhaps lens protection could be of value.
I've owned every phone Apple has sold over the last several years. All phones were in good quality cases and I've never had any issue with the cameras and never have used lens protectors.
Keep in mind anything you put on the lens will make light passing through the camera to the sensor diminished in some way.