I don't have super strong feelings about native v.s. cross-platform UIs, but I think I (and maybe others) think about this question from the "reverse" direction. I expect a given service / app / functionality to work the same everywhere, no matter the platform. This is true of tools I use through my terminal or tools I use in GUIs. Other approaches feel to me like they make using the product more difficult - I may not be able to help someone else on another OS use it, it may mean that an obscure platform has more bugs than a unified approach, etc. I understand why native may make sense, but I do not think it is a given.