Part of Irrational's plan to have you fall in love with Elizabeth was to allow her to be an asset in combat, primarily by tossing you items and weapons mid-fight. The initial version of this revolved around Elizabeth notifying the player she had something and waiting for a reaction from the player to execute, but this felt a little too rigid for the team. Going back to base with a new plan in mind, they wound up making a new system as if the player had an almost psychic link with Elizabeth so that she could offer things to the player and they could accept without having to go through the pain of forcing her into the field of view creating a far more natural and fluid combat experience.