You're a high school librarian (which is definitely of teh kool!), so we hereby give you the assignment to find out directly from the kids themselves.
Believe me, I've tried! We'll have kids come in and ask for a book that we don't have, and we'll order a copy of it for them, but we'll also offer to download a copy onto one of the school Kobos. They'll either say, no, thanks, I'll wait for the real book, or they'll take the Kobo and then come in every day to check if the real book has arrived. (It's a rural school, no nearby bookstore, so almost all of our books come mail-order).
I've asked them why, but most of them just shrug and say they like real books better. (That's the wording they usually use, 'real' books). I'll say, yeah, okay, but
why? and they look at me like I'm a martian.
And sometimes, I don't mind. We had one male student who was a walking billboard for my 'boys read too' campaign. Good looking, athletic, popular, and a CRAZY reader. Just fun stuff - YA, a bit of fantasy, but if a new book came in any genre and I wasn't sure about it, I'd hand it to him and he'd come in the next day with a review. Anyway, he'd read e-books if what he wanted wasn't in print, but with him, in order to make his 'walking billboard' function more effective, I generally tried to suggest physical books, so it would be crystal-clear to the rest of the kids that, no, he wasn't just playing with an iPad, he was, *gasp* reading. I started only giving him books that we had several copies of, because as soon as the kids saw him reading one, they'd want to read it themselves. An e-reader wouldn't have worked for that - they'd have had to speak to him to find out what he was reading, and he was apparently too intimidating for an actual conversation. The turkey went and graduated last year, though, so I'll have to find a new candidate for the job. (okay, sorry, I digress. Don't get me talking about my library!)