not sure what countries you go to but the spots I've been they take the book out and go through it and some countries put stickers on the book too.
Also as mentioned I use mine like a wallet so I have other things in my holder than just the passport.
Never heard of stickers on the book, I’ve only had mine stamped on the pages so I’ve never been in a situation where they would have had to have taken it out the sleeve
If you use it as a wallet I can see why you’d have to take it out since you don’t want to give them ALL your stuff in there. Mine would simply be a passport sleeve, kinda like a book cover from back in the day.