Google does this for the same reason coca cola advertises during the super bowl. It's not because they're afraid of competitors. It's to reinforce their position in your mind as a household name.
Truth is, if neither brand doesn’t keep fighting for their top position they will lose it to competitors.
The walls are being pushed from all sides, but both Coca Cola and google has the strength to hold up those wall. But that doesn’t mean the push is insignificant.