omg this took me sooo long to find, was also driving me nuts!
When you go into the message and then select the images button to choose a photo, look at the bottom right of the screen. There is the little link share logo in light blue. This is a button, just press it and walla!!! So glad its gone!!
If I had to guess, I'd say for the same reason they don't let users know that when you install a major update to the OS on any of their mobile devices, many, if not all apps are set back to factory defaults. This was the case on my Active 2 watch; the latest Tizen update turned of location tracking (the default) and it took me a while to figure this out. Now I am conditioned to check all my critical apps after they send out any update.