In Safari at least clicking a rss link prompts you to open it in a rss reader, which I think is a superior experience. Reading a rss feed in browser is not without use, but I’d argue that that’s mostly the job of the site itself.
The sites sometimes want to provide some special formatting on top of the RSS without modifying it. For example, you might point people to available RSS readers which may not be installed or provide other directions to end users. RSS feeds are used in places other than reading apps. I've seen people suggest that this transformation could be done server-side, but that would modify the RSS feed which needs to be consumed.