UR44 Outputs and extending

Hi, just wondering how can I put to use additional outputs on the back of the unit?
I have my monitors connected but how are additional 2 outs different and what would be a good use for them?
Is it just for additional monitors or is there more to it?

On that note is it possible to use ur44 to extend another interface somehow, or use another interface to extend UR44? I guess not since both can’t be active at the same time and there is no spdif.