It's niche because some companies decided so.

you used to have native RSS support in browsers, and latest articles automatically in your bookmarks bar.

If you design for email alerts you invite reply loops, permanent delivery failures, and all the headaches of scaling SMTP. RSS, while nerdy, offloads almost every operational hassle to the client and works fine for polling when instant delivery isn't mandatory.

Some users want to pipe these updates into scriptable things like Slack, bots, or custom dashboards, where RSS is much easier to handle than email. If you offer both, people will use whichever fits their workflow, and that isn't always predictable.

I added my employer's website RSS feed to the all-staff Slack channel. I find it useful, I don't know about others but no one has grumbled.

https://slack.com/intl/en-gb/help/articles/218688467-Add-RSS...