Unlike Github's mostly developer centric issue mechanism, Jira is more suited for organizations the would have a QA department, a security review, a more complicated release process (multiple phases of validation and testing) or that that just need a custom issue state machine.

It just so happens that those companies also have money to buy Jira licenses and Atlassian is brilliant for letting OSS project use it as well. So they get a foot in the door at multiple places in the industry.

If startup developers don't like it, oh well, there is enough money for them to be made in the Enterprise market.

(Also, I noticed that there is an interesting plugin market for it as well, once you have audience that paid so much to use it, they'll be willing to shell out a a few hundred more for say Slack integration or other such plugins).

Up to you if that's a bug or a feature.

The interesting thing is that it is very often used for Agile project management. It's massive overkill for that. It has the feel of something that evolved from an issue-tracking system, because it existed before Agile and morphed into an Agile tool.