Garbage

What makes someone throw their trash in a can instead on dropping on the ground?

Caring.

Why should anybody care about throwing trash on the ground? what’s in it for them?

Nothing really.

But those who still decide to throw trash in a can regardless of gains, you did make an impact. The environment is cleaner, people have fewer disease because there are less rats, and you feel happier.

You get more out of that than just money.