XP for Treasure
Many of you who have never played TSR era D&D have still heard how you were awarded XP for treasure. This was true. You might get 100xp for the monster, but 500-1000 xp for the value of its treasure. This changed with WotC (well, started to in 2e, but was still an optional rule). People tend to act in ways that foster the reward. Basic human psychology. We do things at work that we are rated/rewarded on. Same for games.
I would encourage questioning that truism.
My memory is foggy cause I was a kid during 1e/Basic, but I don't recall many conversations between us players about "oh, we'll get more XP if we take this course of action, so let's do it instead of that." Maybe we were outliers.
There are many forms that rewards take, speaking about gaming, but this is true in life too. Otherwise if the reward of "academic excellence and recognition" were paramount, psychology would tell us that no students would engage in truancy or go party in lieu of studying. Similarly, if the reward of "high job rating" were paramount, a professional would never engage in pro bono or volunteer work if their company didn't have a program to improve their "job rating" for doing so. And ...well... I have seen plenty of examples of partying in lieu of studying & professionals giving up their time to help others without recognition.
Instead, what's more true IME is that players respond to certain rewards more strongly than others. AND this fluctuates from player to player, and even within the same player from day to day, or even hour to hour.
"I killed it for the XP" might be true one moment, but "I killed it to instigate something and start a riot" might be equally true another moment.
Similarly "I took it for the XP" might be true for one player or in one moment, but "I took it cause I want to draw from the deck and see what happens" or "I took it to keep it out of the evil high priest's hands and/or for leverage" might be equally true.
Player actions, IME, don't always map to what the game says (or the GM assumes) is the obvious reward.
This is why designing good hooks for published adventures is so tricky, and making the wrong assumption can ruin an otherwise good adventure (such as players are motivated by killing monsters, or players are motivated to acquire treasure, or players are motivated by acquiring XP)