Tip splitting or sharing can work well if done properly at the right establishment. First, since a cook's work is partly responsible for the enjoyment of a meal the practice of a waitperson tipping out the kitchen staff makes sense to me, and it's usually just a small percentage (they make a higher base wage generally).
My local hangout is a small place with normally one cook and maximum two wait staff/bartenders in the evening. A couple of months ago the staff turned over fairly rapidly and the owner saw an opportunity. All servers at the bar or on the floor can and do serve everyone and tips are divided evenly. It's a small place and if two staff are on but everyone (us regulars) are all gathered around the bar one server got burned while the other cleaned up. The owner went out of her way to hire staff that get along really well and anyone who isn't a team player doesn't make it past the probation period. Service has gone to great levels and on average everyone is earning more at the end of the night consistantly.
Think...can you imagine a large establishment where customers at the end of the lunch period are all queing up to tip the bartender, the waitperson, the cook, etc? It would be chaos.
They do include the gratuity. They now look for an additional tip.