Game designers might make all the rules, but that doesn't mean you have to play by them.
What's that? Press X not to die, you say? Bah! You're not the boss of me, and if I want to fall into this spiky pit, I shall! There will always be players that embrace the rebellious devil inside them, bending a game's rules to breaking point to see what they can get away with, or ignoring the paths the game is pushing them down. In Issue 277 of The Escapist, Peter Parrish suggests that more players should give it a try, and more developers should embrace and even encourage their efforts.
Player agency, then, is a manifestation of our desire to rebel against a creator. It's the serpent in the Garden of Eden, whispering to us that the designer is keeping something from us and that if we only act against his wishes, these new paths will be revealed to us. God may have given Adam and Eve free will in the Book of Genesis, but it was the Devil who encouraged them to truly exercise it. We should all take a bite from that apple - unless prompted to do so by "Press A to eat." In that instance, we should instead try to escape over the walls of the garden by stacking all of the animals in a big tower.
This is a two-way deal. Some designers are on board with providing as much player freedom as possible ... It's the reason why Deus Ex still holds up as a must-play game ... Some make the mistake of thinking the genius of Deus Ex rests with the choice of taking three distinct paths: stealth, violence or wits ... but it's also possible to create a JC Denton with super-speed legs who's also a heavy weapons and hacking expert. When you're leaping around, popping off rockets, aided by some hacked bots, it's not really a "path" you can fit into a neat little box. And that's the point.
The rebellious player must be careful, however, that he or she doesn't allow that defiant streak to become a tool that a canny marketer can exploit for their wicked ends. You can read more about it in Parrish's article, "The Devil Inside."