The Concorde was cramped. JFK to Heathrow took five hours (3 in the air, an hour in each airport) plus the time for first and last miles. JFK to Heathrow today is 7 to 8 hours with the same provisos.

If you're going to spend a quarter of the day travelling, why not spend a third of the day and do it more comfortably?

The F-35 isn't the fastest jet; fighter jets aren't business jets; apples are not rutabagas.