Different UIs means additional complexity for your testing. How do you make sure that your software still looks and works correctly on all platforms? For web application, the same is true, it is just not called operating system but browser. Supporting 3 or more platforms means additional testing. Every platform needs to be tested.
TestResults.io provides you an unlimited scalability, i.e. run all tests at the same time. Combined with our intelligent cross-system Visual Testing you are ready to not only support additional platforms but to own them.