Although my reasons for it have always been for either important or (admittedly) self-serving reasons.
The important reason: During uni, I read for the kind of subject that had multiple classes studying book-length works, so I learned to juggle having up to 4 classes with required reads going on. I somehow kept them straight, but it wasn't always easy. After that one semester, reading two books at a time has been nothing.
The self-serving reason: Amazon has a reading insights page that tracks your reading. You get perks for reading Kindle e-books through it, a record of how many days/weeks read in a row, or little "achievements" you can earn for reading their ebooks by number of books, frequency, and so on. You don't get paid for any of this or store credits or any of that. Just the personal goals fulfilled thing. For me, it keeps me on track to read at least a bit of something every day, no matter what.
So I'm always reading a Kindle e-book, especially if I have something else to read that isn't Kindle-friendly. It doesn't mean I'm not reading on my Kindle Fire tablet--I almost always am, but I have a bunch of ePub books that don't count toward the achievements. That's why I schedule my yearly TBR taking that into account.
Yes, I plan my reading for the year. I'd never get through my TBR pile if I didn't.
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