Why? file name is not a part of file data? does it depend on file system?
A file's name is a property of its attachment to a directory, not a property of the file itself. With traditional UNIX filesystems, the same file can be attached to more than one directory, with a different name in each. A file doesn't even have to have a name -- if it's not attached to any directories, it is nameless.
However, if it was desirable, programs that compute the has of a file could take into account the name by which they accessed the file. This just wouldn't be a very useful thing to do. It wouldn't make sense with the way people typically use hashes.
For example, "foo.bak" would never have the same hash as "foo", even if it was a backup of it. And identical files with different names couldn't be detected for de-duplication purposes.