In Order to Make the iPhone 4 Cases Replaceable
No matter how you try to turn iPhone 4 cases, you will always have to sacrifice quite a lot of space with iPhone 4 cases. If you look inside the iPhone 4 you will see that it’s practically crammed (hell, they didn’t even have space for an antenna).
In order to make the iPhone 4 cases replaceable you will firstly have to reorder all the internal components in the device so that the iPhone 4 cases will be protect at all.
Secondly you will have to add some margins between the iPhone 4 cases and the internal components so that the user doesn’t damage the phone when changing your iPhone 4 cases.
Thirdly, you will have to add even more amount of padding on the iPhone 4 cases itself so that it can be safely removed without blowing up . Then there are the connectors on the iPhone 4 cases and the phone that take up space.
And lastly, there’s the actual cover on the phone that needs to be removable which also wastes some space.
Most likely those Samsung and LG smartphones you are thinking about have a lot smaller cases and there by shorter cases length than what they would have had if they had non removable cases.