I am curious why a lot of websites use the mobile style "pull out" menu on desktop versions of their sites. Is this for a consistent UX? Something else? Lazines

I am curious why a lot of websites use the mobile style "pull out" menu on desktop versions of their sites. Is this for a consistent UX? Something else? Laziness? I personally do not like clicking on something small on the corner to get the menu for which there is plenty of space already on my screen.