Most browsers don't natively support RSS. If I want to view RSS in Chrome, I need an extension to do so. And that is the same with most browsers (Maybe only Firefox does). The reason for the RSS icon isn't really so you can click it and you're suddenly using RSS. It's designed to be an indicator that there is an RSS feed available, and then the visitor would make the decision to put that in their preferred RSS client. By the same token, RSS clients aren't typically web browsers. So even if what you were asking for was possible, you'd be effectively hiding the RSS icon from everyone.