Often, app developers will focus solely on the technical development aspects like coding, testing, and maintenance. Content creation tasks are sometimes outsourced to specialists like:

- App marketers - Responsible for the overall marketing strategy including ASO, social media, promotions. They may write promotional/explanatory content.

- Technical writers - May assist with or fully handle in-app instructions, help documents, release notes. 

- Copywriters - Dedicated to crafting compelling app store listings and marketing messaging. 

- Designers - May provide visual assets but not write associated descriptions.

- Localization specialists - Translate app/store content for global audiences but don't usually author original copy.

So while some developers handle all aspects, it's common for content-related work to be split out to dedicated professionals for a few key reasons:

- Developers stay focused on engineering priorities over branding/marketing.

- Writing high-quality copy requires different skills than coding. 

- Outsourcing frees up developer time and budget for core product work.

- Specialists can optimize content strategies over multiple app projects.

So in short - many app developers outsource written content creation to content/ marketing experts so both functions can be done efficiently by their respective professionals.