Why do insert operations at the beginning and end of a list take the same amount of time, regardless of the structure size?

Insert operations at the beginning and end of the list are performed in the same amount of time, independent of the size of the structure, if a linked list with pointers to the head and tail is used:

• Insertion at the beginning: a new node is created, its next pointer points to the current head, then the head is updated to the new node — O(1) operation.
• Insertion at the end: if there is a pointer to the tail, a new node is added after the tail, then the tail is updated — O(1) operation.

Unlike arrays, where insertion at the beginning requires shifting elements, a linked list allows quick link changes without traversing all elements.