This is a brilliant idea! I wholeheartedly agree! It would make things tricky for ebooks, though...
But... But the spine... It's got... THE LINES! And the cover... The beautiful glorious heavenly cover... Bent! Ruined! There's a special place in hell for people who abuse their books this way, and it's the river Phlegethon.
A familiar dilemma for readers...>> this is why i read multiple books at a time, when one finishes, i just pick up another one i started! No moral conflict