Pretty much what the title says. Would likely stop people from complaining they lost their items.
Only flaw I see is if there's a way to duplicate items using this. Then again, there are probably much more than just that.
If you're wondering how this would work, there should be a /gamerule keepInventory (something like that) that if /… … true, would do the trick. Again, the only thing I thought that would be the downside is the possibility of duplication glitches.