I've been doing it for 10 years since I was 19 and if my place was like that I'd be long gone!!
Here as long as you don't cause the supervisors/management any issues and keep your head down they'll leave you alone to do the job. If I had to worry about mystery shoppers all the time I'd be a nervous wreck!
This is reflective of where I am too. Management and even the MD chats to us and banter with us, makes such a relaxed Environment, and in my opinion such a environment improves staff performance.