We are tool makers and users. We evolved to be this... we are not alone in this, but we are (a lot) better at it than any other animals on this planet. And a

We are tool makers and users. We evolved to be this... we are not alone in this, but we are (a lot) better at it than any other animals on this planet. And a tool-maker needs materials, and the best materials aren't available everywhere... any old rock may serve as a hammer in a cinch, but not just any rock can be turned into a sharp hand axe. You need something knappable, like quality flint. Pretty hard to find. Given this, the story that collecting potentially useful materials is an evolved instinct makes a lot more sense than your story. Some of us have it more than others; I find it really hard to resist picking up something that looks like it might be useful and taking it with me. It comes from a place deeper than my conscious appreciation of beauty. Feels like pure instinct.