Phone photos carry more than the picture: the camera model, date and time, and often the exact GPS location. When you share a photo as a file, all of that goes along with it.
Upload a photo to see every field and a warning if it contains a location (you can open it on a map). Removing strips EXIF, GPS, XMP and comments without re-compressing: the picture stays pixel-perfect, and orientation and colour profile are kept.