Why can't files be manipulated by inode?

Question

Why is it that you cannot access a file when you only know its inode, without searching for a file that links to that inode? A hard link to the file contains nothing but a n

Answer 1

Btrfs does have an ioctl for that (BTRFS_IOC_INO_PATHS added in this patch), however it does no attempt to check permissions along the path, and is simply reserved to root.