Its about grenade balancing. If some of the sticky grenades (and I say some because we all know the tripmine sticks but doesn't track) didn't have lets call it "magnetism" they would almost exclusively be avoided since there is so many dodges and gyrational movements that can completely avoid it. Slide and blink are excellent examples of this since this accounts for a majority of the players. A simple button press to slide changes where your hitbox is by a huge percentage and the same is true for blink where you can teleport. Its not true homing or tracking its proximity trajectory.