Kidding aside, my primary use case is reading and annotating pdf textbooks and legal documents. I used a 10.5" iPad Pro for over a year for that and, while doable, not very pleasant for my eyes after a couple of hours of reading. Upgraded to the 12.9" iPad Pro this year and my eyes felt noticeably more relaxed even after 4-5 hours of reading and working on the iPad.
Ideally, reMarkable would make an XL version that closely resembles the aspect ratio and size of a 8.5x11 paper, but I'd settle for something slightly smaller with that aspect ratio.