I live in an area without an organized recycling program and no can/bottle deposit, so in my area, the only way to recycle cans is to go out of your way to collect them and take them to a recycling place/scrap metal buyer. If this couple lived here, I would say that if they can convince people to specifically save cans for them and then go through the work of gathering them and redeeming them, they would be fine, I think.
In a situation like you describe, I agree with you. Then they are actively doing something that while will benefit them also benefits the environment (to a degree, but I won't get too nitpicky on this).