Why is the rate widget (from the Rate module) not showing up? I'm using the Rate module, together with the entity reference module. 

I have a content type let's name it "Gallery". I also created a "Photo" content type, then added a "yes/no" rate widget  to this content type. (c)

In "Gallery" I have an entity reference to "Photo".

Now I'm going to make a View like this: Show all of "Photo"s related to this "Gallery" plus rate widget related to every "Photo".

I created a view with nid as argument to get specific node, and two relation, first one is "Entity Reference: Referenced Entity", and second one is "Vote result". then I added first relation as a relation to second relation.

I added "Vote results:value" as field. So far I see the "Photos", but I couldn't get the rate widgets.

What am I missing to also get the rate widgets to show up?
From the screenprint about "edit widget" in your question it shows that you've created a "Yes / no" widget using the Rate module.

But nowhere in your question it shows for which "Node types" you've enabled your widget. Since you're using the "Yes / no" widget (located at admin/structure/rate/add?template=yesno when adding a new widget), you should indicate the desired "Node types" there for which the rating widget is to be enabled. If you didn't specify (select) any of node type, then that would explain why the rate widget is not showing up".