Right, we need to keep in mind that buying a plane ticket or a hotel stay is potentially very stressful for users. From an interaction point of view, the steps may be similar to ordering food delivery, but the emotional weight is completely different. I remember that Booking.com uses a ton of persuasive design techniques: social proof (N people booked this hotel, ratings), authority (secure purchase, verified by X), etc.
On the other hand, AirBnB arguably owes part of its success to their sleek UI and beautiful photos. Since the amount of money spent on an AirBnB and Booking.com is probably similar, I wonder if this reflects different user demographics. For instance AirBnB users might be younger, more tech-savvy, and richer (more disposable income) than the overall Booking.com user base?
