Any reason why block number or timestamp is not accessible via contract?

[flowjosh]

@makoto and @jsd

• Get the current block:
  fun getCurrentBlock(): Block
• Get a block at a given height:
  fun getBlock(at height: UInt64): Block?
• The block info is:

struct Block {
      let id: [UInt8; 32]
      let height: UInt64
      let timestamp: UFix64
}