Second, you’ll prevent yourself from having bloody shins when you actually succeed in keeping the bar close. You don’t want bloody shins - once they bleed, it’s amazingly easy to break those scabs back open again in successive workouts - and we don’t want your DNA on the bar.
Now, if you’ve never let a deadlift drift away from your shins, and if you’ve never had bloody shins when pulling, then feel free to ignore this advice, but your day will come too, my friend, and when it does, you’ll wish you had a pair of those sweet socks.
