You might be surprised at the number of cameras that are fake, or not actually recording. It largely depends on whether the business has insurance and if the local police actually investigate petty theft.
Convenience stores and gas stations in the US are frequent targets of armed robbery, which is what the security is for, not petty theft. (There may be some that count on camera shells as a deterrent rather than having live cameras, but if so it has nothing to do with whether the police investigate petty theft.)
