Why companies that create native mobile apps are forced to make duplicate versions on other platforms? I am not computer savvy, so forgive me for asking why companies that create native mobile apps are forced to make duplicate versions on other platforms. "Duplicate" means the "same", so it means those companies don't have to modify the original version of the native mobile app for other platforms. I am guessing "other platforms" refer to other types of smartphones ... The question is based on the following statement. Please let me know if I have posted on the wrong forum. Thank you!

"However, this type of app is expensive to develop because it is tied to one type of operating system, forcing the company that creates the app to make duplicate versions that work on other platforms."
Duplicate here refers to the functionality only.

Imagine you were making a row boat out of oak, or out of pine... not quite the same thing.

Android and iOS platforms in particular encourage you to program in different languages, Java or Swift, which can be very different for highly complex apps.