No, it's because of CAP forces to make a compromise. If there was a way to be available and consistent there would not be overbooking. But they chose availability because losing sales is worse than dealing with overbooking.

Exactly same with Amazon, they will not bother checking that the product is actually available because then you will miss the sale when the warehouse service is down or slow, which it would be all the time because it has to be a single place of failure. Its better to refund orders for non existent items than to miss sales.

Consistency requires single source of truth which implies single place of failure. There is tremendous cost to it, it's not done for no reason like you say.