The designers spent a lot of time to create mobs, chests and bosses in the vaults. As a casual player I start to clean the mobs one by one to reach the boss and get the chest. I play the vault as intended.
In reality when I made a great progress in the vault, somebody just enter, run to the boss kill it with his beefy pet and get the end chest. Despite I spent my time to get the reward, somebody gets it instead of me. It happened with me at least 10 times.
This not only ruin the game, but repel to do a vault.