Explain the real world benefits of CC cashback

I have a CapitalOne card with 1.5% cash back, no restrictions. I can cash it out, cover past purchases, etc. I’ve had this card for years and have never seen a meaningful return. We all know that no profitable business is giving anything away for free. Where is the money actually coming from? How can I make the most of these “returns” or bonuses?

Maybe 1.5% is just too small. I mean, sure I guess it’s “free” money, but are people really spending $2000 just to make $30?