Jump around? - The idea, which you’ve probably witnessed, is to jump around like a crazed pogo champion in order to avoid bullets and confuse the enemy. This isn’t always effective. In fact, you’ll often confuse yourself more than your enemy, and if you lose track of your opponent’s location, it’s all over. Not to mention, slowing down a bit can keep you off your enemy’s radar.
That said, jumping can be effective, especially when you jump over the head of an approaching enemy. In the time it takes them to turn around, you’ve already started shooting, or have jammed the butt of your gun into their occipital lobe.
Also, jumping around a bit can help alleviate pesky sniper problems, at least until you get to cover. If you’re interested in the advanced technique of tactical jumping, which involves parkour-esque leaps between ledges that are most useful for making quick escapes or finding hiding spots, take a look at the video below (apologies for the music).