Because the filename is no tag data. Only you know that it has the structure of ARTIST - TITLE.
So give MP3tag a clue and import it with the function Convert>Filename-Tag.
See also the HowTos on importing data:
Because the filename is no tag data. Only you know that it has the structure of ARTIST - TITLE.
So give MP3tag a clue and import it with the function Convert>Filename-Tag.
See also the HowTos on importing data: