I worked for LUSH for nearly 4 years. Trust me: "Happy and nice" and "Extroverted" are not synonymous. We don't have to be loud for customers to think the products and company are fun. The introverts at LUSH are burning out because some managers won't let them be themselves.
You can be an attentive, kind, knowledgeable, and even energetic sales assistant with great UPTs, without putting on a loud front for the customers. Not only do A LOT of customers not want that, which shouldn't be news to LUSH at this point, but they can tell when someone's faking it.
- Bullying of multiple members of staff by a supervisor was completely ignored. Even though the management agreed that her behaviour was completely unacceptable, she worked comfortably and without so much as a meeting or a warning as reprimand.
- Management compared themselves to us and expected us to dedicate as much outside time to the company as them, (e.g. to constantly study LUSH and memorize up-coming products), which some of us just don't have the time to do. If LUSH was my entire career and I was receiving career wages, I absolutely consider it my duty to memorise at least 3 ingredients in 20 products in just a few days too, but if it's a 3 day job getting you through Uni or other commitments, then that's an unfair expectation.
Also, some people such as myself, learned much more efficiently on the job than by reading a booklet.