I didn't mean to imply that Ubuntu can't do native apps. It's just that, they probably won't get very many native apps. Top 50 is not so many, and probably not attainable.
As for maps, It's not the app that's hard -- its the data. It's updating the data, all the time, for ever. The app in the screenshot is probably using a data source (google most likely) that Ubuntu won't be able to use in the real world.