> By building an application and putting it in the hands of the business as often as possible.

Just putting the application in the hands of the business is not enough, you need to ensure that you're actually delivering value to the business. You need pieces of functionality that you know the business values (and where both sides understand what the valuable thing is) - i.e. tickets.

> Thirty years ago I used a whiteboard.

> I never needed ticketing software to build software or to ship software.

I'm sure I could keep it all in my head, but I'd rather spend that mental capacity on more important things. That you found a whiteboard useful says that tooling can be helpful - and Trello can be more convenient than a physical whiteboard.