Cop here. Heres the rundown on why we do what we do

We usually use our cars and our emergency lights to serve as a buffer and a warning to oncoming drivers of our presence. As you see in this video, we use very bright LED lights that can be seen for miles even in the day. Those aren't that useful in front of the car we are pulling over. We normally also normally position our vehicles over to them left or cocked somewhat sideways to make the police vehicle the first to get hit rather than our bodies. And the cocked stance may deflect a vehicle away if it sideswipes the patrol car. Still, traffic stops are very dangerous. About a dozen or two dozen cops die each year from being struck by cars or something to that effect.

Additionally, we can write our tickets and do system checks from our vehicle while keeping an eye on the car in front of us. And at night we normally "spotlight" the vehicle to give us the added advantage of seeing into the driver compartment.

However, a lot of times we will pull semi trucks over from the front as it is safer then walking the entire trailer and we can see the driver better. And also because a lot of semi drivers won't really see or hear us when we are trying to pull them over from behind. So there is some flex in how US cops pull vehicles over.

Also, this driver seemed drunk to me. There were subtle things I noticed that made me think there were some impairment involved.