Well, this has been discussed before. Here is the main problem with locked chests: are they destroyable? If so, that defeats their purpose. If not, what is to stop a player from building a fort made of locked chests?
The fact that making a locked chest would probably be a pain in the butt. They would have to chop down 8 times as many trees for their house, along with whatever block is used for the locking mechanism.
Well even safes would have to be breakable (perhaps yielding iron bars) because every block in the game is. Maybe something like it will only break with TNT. That seems pretty similar to real life, anyways...
There's no need for lockable/passworded chests because the only thign taht does is make it harder to open.
Anyone who cares to can easily get enough gunpowder for a block of TNT. Sometimes one night has provided me with enough for, what, 5? Thats, from one night, 5 safes I can break open, which is idiotically easy, and, thus, makes the "safe" useless to anyone who can kill a couple creepers.
However, if we make them unbreakable, easy explotation. Cover the spawn point in them, suddenly, no one is able to get into the map.
uhhhh, so what? Even if you can open the safe with TNT that's still a night's work for something that before would take you a second. I think that's worth it, especially if you are not at your base and someone else is trying to steal your stuff---it gives you more time before they actually get to it.
It could be worked out so it takes multiple TNT blasts to break, or requires at least 2 TNT blocks touching it to go off at once for it to break, or both. That's more than enough to make a safe worth the effort, imo.
And making them harder to craft, such as requiring double or triple iron instead of just one, would prevent people from building huge walls out of them.