Were there any programs besides editors that relied on on the O_NDELAY file status flag (predecessor to O_NONBLOCK)

Recently, I've been researching on the O_NONBLOCK feature specified in the standard. From what I've seen so far, the predecessor of this flag - O_NDELAY had existed all the way back to UNIX System III. I assume this is because was the only way to "poll" files for IO availability (poll and select didn't exist until the STREAMS and Sockets days). The standard developers chose to invent the O_NONBLOCK flag because it was deemed undesirable to conflict with the return-0-on-EOF semantic. Were there any programs that relied on O_NDELAY? I can think of text editors as one such kind of programs (because they may want to occasionally save backups), but were there others?