I made a chicken coop a couple years ago for some ungrateful chickens that never used it. I think I managed a pretty decent job of it despite my having very little experience with actually putting nails to wood, though it came out looking like crap.
Also, I can think of plenty of reasons to carry a can opener with you. Opening a can without one is difficult, time consuming, you could hurt yourself trying, and a can opener is small enough to fit in your pocket so how can you not find space for it in that giant hiking bag? Might as well grab one and bring it anyway. I agree that you should still be able to open a can without them, but not without any number of downsides (smashing it on the ground takes forever and exhausts you, smashing it with a rock takes a fair amount of time and you risk bashing your fingers for pain and ripped skin that could get infected, stabbing it with a knife takes a small amount of time, damages the knife and you risk cutting yourself badly, etc.)