Right now, mobile seems to be the "exception". However, when you're thinking of other, "less common" stacks, like cloud-based Desktop applications or Browser extensions, new use cases become evident.

Furthermore, we're getting more and more stacks right now, such as wearables and sooner or later AR/VR devices/platforms - hence, the need for such as cross-platform tool will certainly increase. Plus, we also make developing single stack apps easier/less painful, so even then it will (hopefully ;) ) be helpful for people.