By doing this, players can easily donate to whoever they want. Trading becomes much easier and steamlined, and players can agree that "host gets food, player 3 gets ammo" or w/e crazy deals they want to come up with.
For those worried that players would just steal things from your trunk, they can already do that. Rucksacks and all. They will just put it on their backs and log off or switch characters. So for those who are playing with more trustworthy people, this will help things out. Players who are untrustworthy aren't going to be able to screw you over harder with this feature.