There are many closed source applications that have been removed from the Google Play catalog for various reasons.
Often this reason is the cessation of further development and maintenance of the application.
Why don’t these people make the code open to everyone if they don’t need it anymore?
This could bring great benefits to all people, but everything that was once created simply disappears.
It’s a whole licensing thing where they have very little to gain but a lot to lose. Intelectual property is very important in the IT world, companies tend to keep their work for themselves.