This is the reason.

Nothing is stopping airlines from offering 1-click bookings, except that lengthy funnels bring in tons of cash. Ryanair has been a master at this since the beginning of time.

In 2020 I booked a flight directly on Google Flights and the booking was complete before I even realized, it was so simple. I never found that UI again.

    > I booked a flight directly on Google Flights

Does anyone else have the experience where 25-50% of the click-here-to-buy from Google Flights just don't work? Is it bait-and-switch from the carrier?

The underlying systems are old, slow and have multiple layers of caching, plus it’s a huge search space, so you’re never really seeing real-time availability. It’s just the nature of it that a lot of the times the tickets are already gone, though Google used to be one of the most reliable.

It has happened for me many times, so could have some truth here