Of course it's a commercial decision. What did you think it was?

It's easy not to overbook. You just don't sell more seats than exist on the aircraft. All carriers overbook and do so deliberately.

If they can find people willing to delay their departure for a day in return for the small amounts you suggest, why not?

That is called a win-win in the real world. A happy air carrier & passenger. Not such a bad thing. And, if you don't fancy the offer, don't accept it. Someone else will.