How to remove the sidebar in iOS Preview?

I like to read PDFs on iPad (manuals, articles etc.). For some reason, unlike on macOS Preview, the thumbnail side is shown permanently. This seems to me a SERIOUS design flaw: it deprives the user of control over the presentation, wastes precious screen space, and, most importantly, RANDOMLY – which I think is the worst quality of a design – reduces focus without ANY gain (the thumbnails could show up by tipping the screen, just as all other additional controls are and/or show up when scrolling).

Did I do something wrong or is there really no way to hide it?