Most combat and exploration ships have small cargo spaces, 100 - 500 m3. The Giant Secure Container (GSC) only fits in industrial (transport) ships (or bigger), and then the freight containers only fit in freighter-class ships. So, these containers are “too large to scoop” by the average attack / PVP ships that can destroy your industrial or freighter transport to get at the loot inside. Which is why most gank situations also involve “neutral” alt characters with transport ships of their own, come to pick up the loot. This makes them “suspect” in the eyes of Concord police, allowing players to shoot if they catch them, and thus generally promoting PVP.
Otherwise, to your original questions:
Anchoring containers in space was important before the recent age of citadels, because all we had before was Player-Owned Starbases (POS’es). These were comprised of a control tower in space and various processing or ship fitting structures, all inside a shield, but NONE allowing ships to actually dock at them. So cargo containers had to be anchored in space, inside the shield, to provide replacement modules and materials to people.
Nowadays, secure containers are still somewhat useful, because of the Mobile Depot deployable; if you’re in wormhole space, or in hostile space where you don’t have access to a station, you could anchor some secure containers with some gear, and use a Mobile Depot to re-fit your ship while in space. You could take the basic combat ship and multiply its cargo space by using Expanded Cargohold modules, then carry some containers and a Depot into hostile space, then anchor and deploy them as a base of operations, and reconfigure your ship for combat, removing the Expanded Cargoholds to fit armor and combat modules.
Corporations in EVE are the equivalent of player guilds in other MMO’s, and they have shared hangar space in all the stations that they own or rent, that members can use. Access to this shared hangar space is somewhat configurable by the CEO / Directors; they can give “no access”, “view”, or “take” access to each member of the corp. Blueprints are an issue, because ideally you want your people to be able to “use” the blueprint for manufacture but not “take” it. So Audit Log containers keep track of who did what, so that the CEO / Directors can review the log and maybe detect possible troublemakers. Keep in mind that it’s an international server, and the CEO may be sleeping while corp members enjoy their prime-time gaming session.
Standard / Freight Containers
Designed to be transported by industrial transport ships and freighters, respectively, there is no password because this game is a PVP game, and if your ship explodes and spills its cargo, that loot belongs to whomever “won” that battle. A password would interfere with claiming the spoils of war.
Secure Containers Again
The password only works if the container is anchored. Otherwise if you’re transporting a secure container with a password, same as above, if you get killed, the attackers have the right to the loot, so they can bypass the password by just scooping the container into their own ship and then re-packaging it at station. Repackaging takes all the items out of the container and puts them on the station hangar floor.
These are for sorting all your junk, or all of a corporation’s junk, in a station; they’re supposed to work like folders for computer files.