With an extension (or native browser support, which used to be common) this is not the case. Sites with feeds can link to them in their metadata using <link re

With an extension (or native browser support, which used to be common) this is not the case. Sites with feeds can link to them in their metadata using <link rel="alternate" href="...">. This would cause a subscribe button (usually the orange RSS logo) to light up in the user's browser. Clicking it would automatically submit the URL to the user's preferred feed reader (or if there were multiple linked feeds, let the user choose one).