If a store says they are open 24-7 why would they have locks on their doors?

If a store says they are open 24-7 why would they have locks on their doors?
Because... The landlord installed it many years ago, before this 24-hour store signed the lease.
Sometimes, when the clerks work alone, they also need to go to the bathroom. So that you can lock down in emergencies, such as tornado warnings, or lock down situations or when they're doing construction. They can lock up on holidays such as New Years Day and Christmas. For occasional, temporary down time such as inventory control. Doors are made that way. They are are manufactured with locks. You can't buy an exterior door that doesn't come with a lock. Stores are made that way. In designing a store you need to consider unforseen events such as emergencies or a future change in store hours. Some stores may abandon the 24-7 schedule years later. Since it costs practically nothing extra to order doors with locks, why not? It would cost a lot more later to add them in. There is an end to every beginning. To close down on Christmas Eve night and Christmas.
The store is required to have locks for emergencies like a bomb threat when all customers have to leave the store, and it's closed for a big part of the night. Many stores, right after getting robbed, will lock customers outside, so that the police can take full charge and investigate what happened with all that missing money. If the store didn't have locks on their doors, the insurance costs would be higher. Many large United Kingdom 24/7 shops are not allowed to open on Sunday nights (due to old laws) and so would need the locks to close on Sunday nights. Many places lock up, if there is a power outage. Some stores used to have regular hours, before they became a 24-hour stores. A store may stay in business for a certain amount of time, then sell to someone else who wants locks on the doors.