Submitting your original, important, unpublished, research to some random entity. I would be VERY surprised if more than 2% of academics think this is a good idea.
Regarding security concerns: there is an open-source version for those who want full control. The free cloud version is mainly for convenience and faster iteration. We don’t store manuscript files longer than necessary to generate feedback (https://www.rigorous.company/privacy), and we have no intention of using manuscripts for anything beyond testing the AI reviewer.