That's because, well, they CAN. And they do. Every single time they set foot on the stage.
The only reason you're being so pissy is because you're sitting at home instead of being at the actual show. If you were actually AT one of these shows, and afterwards the only thing you could say was "LP, you officially suck!" then you'd officially be a douche.
I don't think you'd be thinking that though, I'd like to believe you'd be thinking "wow that was awesome!" If you let the fact that they played a "usual" setlist ruin the entire concert for you and make you unhappy, I'd feel sorry for the people that would have to attend a concert with you.