Yeah I was myself surprised when recently I needed RSS feeds of a few parameters and was pleasantly surprised to see them still inplemented even with API’s on most of the sites.
We created an API at edX that is much more robust than our RSS feed. People still use the RSS feed because it is much easier than (a) registering for API credentials, (b) figuring out how OAuth works, and (c) learning what JSON is and how to parse it. The simpler solution was good enough for many clients.