Then you must not have tried many pdfs because there are many where the reader can't detect the columns. Even when column detection works, you can't increase the font size beyond what the pdf uses as the text won't be reflowed. It's of course an even bigger pita for those relying on text-to-speech to read pfs.
I don't know, something around 1 to 3 per day for the last 7 years maybe, I read and write papers as a living.. I never really had any problem.. I mostly have issues with epub like formats..
Of course tts is a different beast, but.. Try to read science in general with tts.. It doesn't make sense.. And you need time to process each sentence and put it into context.. So even with reflow, tts would be a nightmare for science content.
Epub is great for content that is mostly texts (Novels,…). As soon as there are objects that need to keep their relative distance to each other (equations, diagrams), I go for PDF. It's also not easy to get good typesetting for epub files. I believe that typesetting gives you a visual map that provides an additional memory boost. Doing focused reading on a phone is a no-no for me. I use my tablet for PDFs and my e-reader for epubs.
