Not entirely superseded. UNIX and DOS file systems, and most internet protocols, have great difficulty representing the kind of file that is common on mainframes, where a file is a sequence of records and a record is a sequence of arbitrary bytes, but such files do still exist.In the first decades of computing, there were two kinds of "newlines". One was control codes for printers: carriage return and line feed. The other was record start and end signifiers for tape storage: think COBOL or FORTRAN.
By the 1990s, both kinds of raw newlines had been superseded: drivers hid device details, and Apis took hid drivers. Newlines were for formatting things on screen or for markup.