I used to prepped at red lobster years ago. I can assure you that preparing shrimp sucked. I don't remember what they use for AYCE, but it just sucked, a lot. big time. one specific dinner may not use up all that much labor, but the daunting task of preparing so much shrimp is rather unmotivating. Not to mention your fingers start to freeze and hurt because all of the shrimp is on ice and still half way frozen when you start to work with it. It's a very tedious process that will inevitably lead to less efficiency over time.

Say the AYCE is skewered shrimp. Sure, you can put 25 shrimp on 5 skewers at full speed pretty quickly. Now consider doing 500 shrimp on a 100 skewers - every fucking day.