It’s absolutely necessary…
To know your Java (OOP), Android SDK, and Android Studio
We don’t have a problem with juniors, but there’s no time to teach them everything.
To version the code
Commit, push & pull in Git is as natural for you as brushing your teeth.
To write the code well, so that others can actually read it
We have our own code style and prefer to keep the spaghetti on our plates.
To handle an API well
You can parse JSON or XML from REST API into the database without spending ages going through the documentation.