Phones are a really bad analogy as they are effectively designed and built to need a case (e.g. iPhones with a glass back are just asking to be cracked) - built-in accessory/money making thing in my opinion.Beg to differ. I also have a Petrel2 with a chunk/chip missing from the battery compartment. They may be tough, but definitely are not indestructible.
The the silicone cover does help reduce shock, as evidenced by untold billions of silicone phone covers. No need to be so ridiculously contrary on an obvious issue.
I see no value in adding extra bulk with a silicone sleeve on my Perdix 2 or Teric and am not concerned if I get a scratch (have not though). However, as others have said, it’s your money/your decision so buy what you want.