There are 3 types of storage in BE 2012
1) Disk Storage - This is managed by DLM. See this blog
2) Disk Cartridge Device - These are storage on removable disks, like RDX disks, USB flash drives, etc.
3) Tape Cartridge Device
Since Disk Storage is managed by DLM, it does not need any media sets and thus vaults. If you only have Disk Storage defined, then you would not see media sets and vaults in the Storage tab. As these are not need in your situation, these are hidden away.
Only when you have defined either Disk or Tape Cartridge Devices, will you see media sets and vaults.