1. Because this only works for the Apple camera, not other photo apps.
2. because it is insecure (as previously stated)
3. Because it is unreliable (as previously stated)
4. Because it takes up disk space on ALL your devices (as previously stated)
5. Because it consumes enormous bandwidth (as previously stated)
I'm just reiterating this for you. I and others have made these points previously. It isn't working properly the way you suggest. Not sure how to make that clear.
Emailing or Airdropping to oneself involves selecting images individually as there is no select all feature. Also, Airdropped files are not filtered. It's the same issue. This is mind numbingly time consuming and tedious when selecting a lot of photos. The feature is only useful as an ad hoc service for a small number or single images, not as part of any regular workflow. We've come to expect technology, especially Apple technology to improve our lives and create ease. The above issues are due to a seemingly built in retrograde step of disallowing simple tethered transfer any more - for no good reason. However, we are asking this as practical question, not as a philosophical one on this post. I have provided the reasons why as a courtesy to you. Some are practical, some are privacy based. It is, I agree an interesting and complex issue. I also appreciate that method works for you, but it does not copy all of my photos when I do it that way (notwithstanding the security and privacy as well as bandwidth and disk space usage issues) - hence the need for 100% reliability of a cable. I personally don't want or need images on a cloud either (again irrespective of the concerns above and I personally find the whole forced loop utterly counter productive and 'aggressive' and ungenerous by Apple in it's implementation). Ever.
The original question still stands, unfortunately so.
The current result is a complete mess of photo organisation and transfer. Some are in the photo stream, some are not. Some are in the camera roll, some are not. I also have a couple of stragglers shared to the iCloud drive for export. Some are in the last or recent imports in iPhoto (and now Photos in an attempt to try that method, which also does not boring over filtered images), so I have photos in five places. All these sources need to be checked so as not to accidentally delete an image that is not in the other library/location. This all occurs because one cannot transfer simply and easily via a cable any more.