FWIW, meerkat...

A bunch of colleagues and I were traveling a few months ago, and I noticed that a lot of them carried their passports in a protective sleeve. "Why?" I asked. Well, apparently if the photo page starts coming apart at the laminate (which can happen when your passport is bumping around somewhere) it can become unreadable for those little passport machines and then has to be replaced. I ended up getting a cheap passport holder just to protect it.