Why is it impossible to repeatedly call some HTTP methods without changing the server state?

Some HTTP methods, such as GET, are considered idempotent, meaning that repeated calls should not change the server's state. However, methods like POST usually change the state and do not guarantee idempotency.

The inability to repeat certain methods without changing the state is due to these methods being intended for creating or modifying resources (for example, creating a record in a database). Repeating the call can lead to duplication or other undesirable effects.

This is related to the semantics of HTTP: methods that change state (POST, PUT, DELETE) are not always safe to call repeatedly without control, as the server may change data or state with each call.