Frames were widely abused by early web apps to do dynamic interfaces before XHR was invented/widely supported. The "app" had a bunch of sub-frames with all the links and forms carefully pointing to different frames in the frameset.

A link in a sidebar frame would open a link in the "editor" frame which loaded a page with a normal HTML form. Submitting the form reloaded it in that same frame. Often the form would have multiple submit buttons, one to save edits in progress and another to submit the completed form and move to the next step. The current app state was maintained server side and validation was often handled there save for some basic formatting client side JavaScript could handle.

This setup allowed even the most primitive frame-supporting browsers to use CRUD web apps. IIRC early web frameworks like WebObjects leaned into that model of web app.