I'm sure Apple can design a rugged phone if they wanted to. A rugged phone designed with shock/vibration/drop protection in mind is not the same as a fragile phone with a case on top.

All kinds of ruggedization are wear items. Even a bicycle helmet needs to be replaced after it has experienced an impact. They should be easily replaceable, like phone cases are now.

There are many designs possible, I don't understand why you want to shoehorn an unsuitable design meant for providing protection to the human head onto electronics. In any case, this is a good discussion, we know what to avoid so yes - we don't want to have a design that necessitates replacing the phone.