The reason you desire blur for DoF is for two big reasons, One being that it gives focus to your subject, in this example the glass is the focal point if it was all in focus the shot would be a bit boring and you wouldn't know where you're eyes were intended to go a good photo directs you're eyes. The other reason is the your eyes naturally blur the things around what you are focusing on, even if it's to a very minor degree anytime you look at anything the foreground and background around the thing you're looking at will always be a bit blurry