Lifters also have another purpose: they provide stability by connecting your feet more "solidly" to the ground. Other gym shoes (cross-trainers, running shoes) have padding in them... which is awesome for running but that squishiness can translate to instability when you're literally doubling or tripling the amount of weight.

Consequently, some lifters who have the ankle mobility will lift without shoes. Given the state of most gym floors, that's a no from me, dawg, but hey to each their own.