The wide grip tends to round the shoulders forward (which is dangerous), whereas the close grip naturally pulls the shoulders back and puffs the chest out.
There seems to be different opinions on this
Dave tate says- [quote]
Mistake #2: Pulling the shoulder blades together
This is a mistake I made for years. Stand in a deadlift stance and pull your shoulder blades together. Take a look at where your fingertips are. Now if you let your shoulders relax and even round forward a little you’ll see your fingertips are much lower. This is why we teach a rounding of the upper back. First, the bar has to travel a shorter distance. Second, there’s less stress on the shoulder region. It’ll also help to keep your shoulder blades behind the bar.[/quote]
Mike Robertson- [quote]
I can tell when a powerlifter is going to miss a lift before he even attempts it. That’s because he starts the pull with his chest caved over. When this happens, the bar gets out in front of you and your low back has to work overtime to get the bar back in the groove. You end up doing what amounts to a straight leg deadlift. Instead, force the chest up from the beginning [/quote]