people who otherwise would have gone their entire lives without ever hearing about encryption were exposed to the term and the marketing convinced them that encryption and privacy was a valuable thing, even if they didnt fully understand the mechanisms or why e2e might not necessarily be very effective in specific circumstances.
later, when presented between option a and option b, where one has encryption and the other doesnt, they are more likely to choose the one with it ("well, if instagram and facebook use it and say it is good...")
between signal and plain text, it is easier to convince friends to use signal if they see positive marketing about encryption on other popular apps they use. it is easier to convince them to encrypt their backups before uploading them to their google drive. hell, its just a good conversation starter to introduce encryption/online privacy to people that never really think about it. that type of thing.
those same friends are not going to use irc regardless. not really a loss if it was never even on the table.