Keyboard interaction in menus

Hi there,

I am seeking for help to understand the impact of issue with the keyboard interaction  in the menus on the web.

As mentioned at https://www.w3.org/WAI/GL/wiki/Using_ARIA_menus, it is required that the menus on the menu bar should be navigable by using arrow keys, but this is not in practice for majority of websites, so is it a violation of 2.1.1, or it is more of a usability issue?

As a matter of fact it would be good to have similar keyboard interactionfor the widgets on desktop and as well as on the  web, please share your thoughts.

Regards,
Ajay