¿Puede (usted) pasar el menú, por favor?
 

¡Hola!

When we say , pass the menu please

Why don't we use : (¿Puede usted pasar....? ) , instead of : (¿Puede pasar ?) which
doesn´t define the third person properly ?

I understand that in such situation you are talking directly to the meant person , But , Iḿ asking this question from a (grammatical) point of view.

¡muchas gracias!

That's not a grammatical difference, but a situation defined by a context.
If you want to read the menu, the person who should pass it will not expect you to talk to anyone else.

If you use the pronoun, you're not being more explicit in this case, but more polite by addressing the person and distinguishing them immediately from the rest of the world.

¡Muy claro Angelica! :)

Gracias desde Egipto :)

I guess it is the same thing in English.

Pass (me) the menu.

Will/would you pass (me) the menu.