The one tangible usecase is perhaps booking things. But, personally, I don't mind paying 5-10% extra by going to a local store and speaking to a real person. Or perhaps intentionally buying ecological. Or whatever. What is life if you have a robot optimize everything you do? What is left?
I love talking to real people about stuff that matters to them and to me. I don't want to talk to them about booking a flight or hotel room.