First of all I want to make it clear that this is just a showcase/demo product. It's definitely not something I'm planning to sell.
Additionally, it's not even remotely production ready, and it's missing about a zillion features that would make it a full-fledged project management software.
The main reason I built this was to have a good showcase for potential future clients.
The second reason was to share with the community. More specifically to show how to organize non-trivial React projects and to provide folks with a bunch of React code to learn from.
The third reason was to improve my skills and get better at working with hooks, TypeScript, and a couple of other things.
Back when I was learning React (4 years ago) I was a bit frustrated by the lack of non-trivial example projects. It was either a bunch of to-do lists, or hugely complex codebases like https://github.com/Automattic/wp-calypso.
I like to think that this Jira Clone presents a nice middle ground.
Bonus: Here's a Trello clone I built while learning React four years ago: https://boxd.ivorreic.com/ :)