You don't have to self host it if you scroll down there is a list of public instances: https://rss-bridge.github.io/rss-bridge/General/Public_Hosts.html

Reason to self host, some websites don't like rss bridge because it's a kind of adblock from their point of view, and they actively block the ip addresses of these instances. If you selfhost it, you can use these sites, because a single user instance won't generate as much traffic than 1000 users, so they won't notice your instance

How else are you going to use it? Ok they have an hosted instance, but that's not great for privacy and will break as soon as it gets somewhat popular as the sites usually have scraping protections.