It was the first choice for many companies. In the Delphi development world (starting in 1996), NNTP was pervasive and almost every company related to the 3rd party ecosystem ran an NNTP server (we still do, it provides both NNTP and web access to the same message store).

Believe it or not, the issue wasn't as much the servers not being maintained any more, it was the clients. Various clients, especially email clients, stopped providing NNTP support alongside POP3/SMTP/IMAP.