There are plenty of reliable young men who enjoy engaging in violence and will take low-paid jobs in store security. (There are many more who don't actively enjoy it, but don't mind engaging in it and consider being competent at violence an important part of being a man.)
The pharmacy gives its security guards instruction not to use violence because they don't want to get sued when a guard seriously injures a thief: it is impossible at the scale of a chain of stores to subdue and detain thieves without some risk of killing some thief or seriously injuring him.