There are two main reasons to go barefoot when you deadlift:

  1. Less heel lift means you're closer to the ground, which means less distance the bar must travel.
  2. Less heel lift means less anterior weight shift into your toes, which makes it easier to get your weight back and engage more of the posterior chain (hamstrings and glutes).

If your gym sucks and they don't allow you to take your shoes off, you can always opt to wear more of a minimal or flatter shoe like Chuck Taylor's or New Balance Minimus.

Related:  30 Days of Deadlifts

Related:  The Truth About Barefoot Training