Because you are pulling it every day.
Images only download when there’s a new release, so you didn’t answer the question.
The answer is: Because Jackett has daily releases. Maybe they don’t version their releases.
Sure, but also, why are you pulling daily to begin with?
Because it’s an automated system which looks for updates daily. Is that a serious question?
Yes, it’s a serious question. Pulling far too often is exactly why Docker Hub is implementing lower daily limits.
You’re suggesting that a single daily image pull is somehow abusive and the cause for Docker Hub imposing limits. This argument is invalid because even after Docker Hub imposes it’s limits, pulling an image daily is well within those limits.
However, I am of the opinion that Portainer shouldn’t be downloading images unless the container is being deployed, if that’s actually what’s happening, we don’t know.
OP is doing nothing wrong, so please refrain from making illogical bad faith arguments.
