To support the fast pace of software development, evolution in technology, and user demand for more features, it is imperative that our software be well-organized and highly maintainable. Any one on your team, or yourself at some point in the future, should be able to easily understand how the code works and quickly make the required change or addition. Supporting this sort of future development requires a well-organized project and an investment of time to maintain standards.

Native applications are typically written using a single language: that of the platform they are built for. This constraint means that an entire application can follow standard layout, naming, and semantic conventions, making it easier to work on any portion of the software. Modularity and code reuse are far easier to accomplish, and so duplication or incomplete changes are less likely to be a problem within the project. Test Driven Development, by now a well-utilized methodology, doesn't require a single language within the code base to work well, but the tooling required to make it possible does vary by language and having only one setup to support per project is beneficial.

One of the reasons that the other forms of graphical applications (mainly web-based) use multiple languages is also why they are harder to test: their interface is presented using a web browser (or embedded HTML renderer), which can vary hugely from one platform to another. Irrespective of the age of the hardware or the type of device it's being used on, people will expect your application to load fast and look right. This means a lot of variation to deal with and a lot of testing for each change. Compare this to a native graphical application, where the target devices are known and fully supported by the toolkit used for developing. Testing is easier and faster, and so changes can be made rapidly and with confidence. Native graphical applications truly are the best way to make beautiful, responsive applications that will spark joy in your target audience.