Why don't you use any other RPC node?

That is what I do. You can choose the node you want to use in settings on SteemWorld. But RPC nodes don't come with all features which I need in my tool. Mentions, follower history, incoming delegations, delegation history, transfer and content searching in posts, comment counts, witnesses produced block ratio, voting stats and many more things are only possible by parsing the chain by myself and storing the data in a fast db on my own servers.

Of course it is possible to develop own API calls, but that would require to run an own full node.