I have a feeling it's a quirk of the billing system - you sign up for an Atlassian system, it goes into trial mode, and then you pay for it if you want to keep it.
But when it's free, you don't need to pay. But I don't think the licence system understands that, it assumes you're going to.
I remember seeing this when I got my free plan. But it just went away when my trial expired. The free plan will just continue when the "trial" expires.