you say that people just want to download an e-book and have it work for them, but that doesn't apply if someone wants .pdf...
Someone may say they want PDF, and you may generate it for them, but it still won't work unless you correctly guess what device and format they want the PDF for. For example, if I want that PG out-of-print novel to print out on my PDF printer in 2-up mode, double sided, center bound, 8 x 11 paper stock, so I can bind my own copy of that novel? Did the PDF you created work for this purpose? Nope. PDF does great for printing out simple short technical documents in 8.5 x 11 format. It doesn't work worth a dang for books, nor for most other paper sizes, nor for other than simple short technical documents - which is why serious content creators don't author in PDF.