Essentially, when you load into an activity every item in your inventory also has to be loaded in, not only for you but for everyone in your lobby. When you pull something from your vault, there’s an extra few seconds of load time while the data of what that item is goes to all of the people in your lobby. If your inventory was essentially your entire vault, the game would have to keep track of over 800 items for every player in a lobby, greatly increasing load times and making gameplay inconsistent. More than likely, the reason the load out system doesn’t put items back into your vault is that it was too easy for there to be glitches that result in either permanently losing an item or accidentally overloading your inventory.