Because Windows Explorer is the wrong way to get photos off an iPhone. Those aren't disks, but Windows Explorer is too dumb to recognize them as what they are, Extensible Metadata Platform (XMP) "sidecar" files that contain the edits of photos that you made on the phone. You should be following Microsoft's instructions:
For Windows 7 and later, use Import pictures and videos. Here are the full instructions from Windows Help:
How do I get pictures from my camera to my computer?
Here's one common way to copy pictures and video clips from your digital camera to your computer:
- Connect the camera to your computer by using the camera's USB cable.
- Turn on the camera.
- In the AutoPlay dialog box that appears, click Import pictures and videos using Windows.
- (Optional) To tag the pictures, type a tag name in the Tag these pictures (optional) box.
- By default, the folder name includes the date the pictures and videos are imported and the tag name.
- Click Import.
- A new window opens and shows the imported pictures and videos.
You can also see Apple's instructions: Import photos and videos from your iPhone, iPad, or iPod touch to your Mac or Windows PC - Apple Support
And this helpful tip: What to expect when you import edited photos from your iPhone, iPad, or iPod to your Mac or PC - Apple Support