When accuracy counts with a rifle, using something to brace off of is critical.
The thing about the real world is there are no shooting benches. There are no chairs setup at the perfect height. In the real world, be it a shooting competition, military, police, hunting, or self defense – you usually have to shoot from improvised positions. Knowing how to best use your cover/support is a very good way to quickly get accurate shots on target.
Want the short reason? Resting your barrel on an object, like cover or a support, makes your shots miss. Good enough reason? Good. Want to know more? The video explains it well.
It is a very obvious statement to say that your rifle’s sights are above your rifle barrel, usually about an inch and a half or so, be it iron sights, red dot, or variable optic. However, it is still common to forget that when shooting over a barrier, like on a vehicle. This can result in bullets going through the barricade and not hitting the target.