Because not everybody is comfortable with carrying used sanitary pad / tampon / earbud / cotton pad through the flat, especially in the presence of the guests.
Even guys sometimes used pads if they have incontinence and don’t want to parade with dirty and smelly package, letting everybody know they have medical conditions.

All of these products shouldn’t be flushed.

Theoretically “naturalia non sunt turpia” but still some people prefer not to share all the aspects of their physiology with others

Also - often bathroom / toilet trash can are closed, while kitchen one usually tend to be open. Part of the people prefer not to spread toilet smells in the place they eat

In part of the world it’s forbidden even to flush toilet paper.