Making iPhone photos usable anywhere
HEIC is the iPhone's default photo format and much software still refuses it. JPEG is accepted everywhere.
The problem usually appears at the worst moment: an upload form rejects the file, or someone on Windows cannot open the attachment you sent. Converting to JPEG removes that friction permanently for that copy. If it keeps happening, an iPhone can be set to capture in the more compatible format instead, under the camera settings, which avoids converting every time.