Digging into my biomechanics background...
Sports in which you look at a target tend to be ones in which you are holding the projectile.
You look at the dart board
...the bowling pins
...the catcher's glove,
...the basket
...the wide receiver
Sports in which you look at the ball (or object you are striking) is when you are not holding it.
You look at the soccer ball when passing and shooting
...the golf ball
...the baseball when batting
...the hockey puck when passing or shooting
So, what makes pool different?
We have two targets. Strike the CB, so it moves and strikes the OB. Under the normal rules, we would look at the CB last because it is not an object that we are holding.
HOWEVER!
We have tremendous stability in our set up, our bridge, and our stroke. The cue ball is not moving. Striking it squarely is nowhere near as complicated as hitting a golf ball with a 70-110 mph swing. The CB isn't moving, and we shouldn't be either (other than a very controlled and straight stroke). It is a very controlled or contained action and strike.
For that reason, we can look at the OB even though we are not holding the CB.
DOUBLE HOWEVER...
When striking the CB is more complicated, like a jump, masse, sometimes shooting off the rail, and when tree topped badly, I bet many people do look at the CB last.
EDIT TO ADD: Some golfers that are incredibly compact and dependable in their putting stroke have tried looking at the target (the hole or target line), which is like OBL. But even that stroke has enough moving parts that I don't love it on putts of any meaningful length.
