Because things happen.
Stuff happens. Things break. Lostness occurs. When the item in question is the housing for your Hero3, Hero3+, or Hero4 camera, replace it with the GoPro Standard Housing. Identical to the one your GoPro came with, the casing is waterproof to 40 meters and the pack includes the Skeleton, Touch, and Standard Backdoors.
Item #GOP004S

CompatibilityGoPro Hero3/Hero3+/Hero4 cameras
IncludesSkeleton, Standard, and Touch Backdoors
Waterproofyes, to 40 meters
Recommended Usereplacement or backup housing for your GoPro
Manufacturer Warranty1 year