I very much want to keep my passport intact for the ten years of its validity, so keep it inside a passport holder at all times.
I fscking hate when anyone tries to stick or staple stuff outside or inside my passport.
The only exception is immigration agents, because you don't mess with them.
I request security screeners to not stick anything on the outside of my passport. Same goes for baggage check-in who (rarely) attempt to stick the baggage tags on the back of my passport.
For I-94 forms, I carefully remove them myself in advance before check-in. Check-in agents tend to tear them off of the passport without any care.