why ActivityResultContracts.GetContent()/TakePicturePreview does return file

Question

I am uploading a file as multipart using retrofit

 val requestIdentityFrontSideFileMultipartBody =identityFrontSide?.asRequestBody("image/${identityFrontSide.extension}".toMediaTypeOrNull())
                ?.let {
                    MultipartBody.Part.createFormData(
                        "identityFrontSide",
                        "identityFrontSide.${identityFrontSide.extension}",
                        it
                    )
                }

however

val launcher = rememberLauncherForActivityResult(
        contract = ActivityResultContracts.GetContent(),
        onResult = { uri:Uri ->

val launcher =
        rememberLauncherForActivityResult(ActivityResultContracts.TakePicturePreview()) {
}

ActivityResultContracts.GetContent() return Uri from gallery ActivityResultContracts.TakePicturePreview() return bitmap

I don't understand why ActivityResultContracts does not return files and how I can upload uri/bitmap to retofit without convert them to files because that not working for me