Why are mid wards effective?

On this match between Miracle and w33, Miracle (on the dire side) placed his wards on his side of the mid, center atop the ledge. (2:02 minutes into the vid)

I noticed other high level mid players do this too. Why is that?

I understand he did this so that he could see w33's side of the mid lane, but there are better places to put that ward. For example, at the upper left side of the radiant side. In this way, you can also see the top rune and watch out for ganks, while having vision of the mid lane.

EDIT Here is an illustration of the map, with the red X being the ward placement seen in the vid, and the green X being what I think should have been the better ward placement

Why is the Red X a good Placement for wards nowadays?

Uphill wards like the one you have seen in the match are placed to have vision of your opponent rather than the lane itself. If your creeps are fighting in the river, you have no sight of what is happening uphill.

If you want to prevent being killed by ganks, or have an enemy like pudge, having uphill vision in the midlane is very benificial.

Fitting to this situation: placing the ward on your side of the river increases your chances that it is not going to be dewarded, while placing it on predictable places, a sentry will get rid of your ward.

All these pro players know each others secret places of placing the ward. So it's always useful to change your way of placing wards. If the ward is placed on the green mark then u don't get vision on your side cliff at all at the night time because of the trees. And also since the ward is placed near you so if the opponent wants to deward by hitting it then it's not possible and if you are fast enough to take out the ward with quelling blade or tango. Somehow you just want to reduce the enemies farm since at the start of a game dewarding gives you a huge boost in xp and 50 gold.