It's because people who create these use cases perceive this as a difficult and painful task - but how many people really think about their flights over the day? Pretty sure the majority of Meta users has not flight booked for the next 3 months. I can only assume that this is more seen as a showstopper. Look how difficult this is and how we solved it.

Shopping is another classic. I personally don't want to trust an AI agent with checkout. research is fine, but I don't want the AI to go on a shopping spree or Amazon added some subscription into their checkout flow and suddenly, I'm paying for Prime because my AI agent thought it's a good idea or just missed it.

It's not unheard of that Amazon bundles a subscription into your checkout. So I don't think it's too unrealistic.