Why isn't the 'save image' option coming up when FB is opened in Chrome/Firefox when image keep pressed?

[AC Question]

'save image' option not coming in fb opened in chrome/firefox when image keep pressed.

I have moto x gen 2, updated android to lollipop 5.1
I keep my finger pressed on fb image on newsfeed, it opens options but doesn't include 'save image' option. When I click picture to open and then keep it pressed, no options are shown.
What to do?