I've worked in businesses that had high turnover.
The costs of training employees are higher, because you have to train so many and then they leave.
The atmosphere is worse, because you're just another replacable cog in the machine.
And usually there is high turnover because the work isn't that desirable. This is never a good thing, especially in an industry like waitressing, where the work CAN be desirable. After all, not all restaurants deal with high turnover. Some are highly sought after by potential employees.
I have never worked in a place that had high turnover where the employee work was NOT at a lower level.
I'm thinking of places like McDonalds, etc. where all employees are about at the same level. The place is designed around high turnover. If you took that model to other areas, such as sales, management, warehouses, etc. Would the level of work decline accordingly?