Or a batter with an armguard leaning over the plate so he gets a HBP?

Those sorts of things happen in every sport. It's just -- as is said elsewhere in the thread -- the reward in soccer is much greater.

As for your specific example, though, one might argue that the defense is given every advantage -- thanks to the offsides rule -- to keep the player with the ball in front of them, so when the player with the ball gets BEHIND them, the advantage shifts to the offense. If you've abused your advantage to the point that you're chasing the player with the ball, well, any repercussions are on you. That's not condoning diving, but rather what you describe.

(One could also argue that a player naturally slows when he has to collect himself to shoot, too, btw. So that's a major factor in what you see as well.)