You can, but every hardware feature you add takes physical space in the phone. Making a phone waterproof requires adding stuff to the phone, which takes away space for other things. Usually battery size ends up being one of the things that takes a hit. You want a phone that’s waterproof and has a removable battery? Then the battery size gets reduced by X%, or some other features people care about get dropped.
You can, but every hardware feature you add takes physical space in the phone. Making a phone waterproof requires adding stuff to the phone, which takes away space for other things. Usually battery size ends up being one of the things that takes a hit. You want a phone that’s waterproof and has a removable battery? Then the battery size gets reduced by X%, or some other features people care about get dropped.