Reasons I can think of: - Most people want cheap flights over everything else, speed is expensive - The flight time only has a limited relative impact on the

Reasons I can think of: - Most people want cheap flights over everything else, speed is expensive - The flight time only has a limited relative impact on the overall travel time. Time to get in and out of the airport, security, border controls, boarding, taxiing, etc... often take longer than the flight itself. - For passengers who are ready to pay more, you can always offer more comfort. The advantage with comfort is that you can divide the plane into classes, it is highly modular. Faster requires an entirely new plane design just for those who can afford it. - Arguably, comfort is more valuable than the kind of speed improvement we can get. For example, if you sleep better on the plane, that's less sleep you will need at your destination, saving you time overall. If you can work on the plane, that's also time you don't have to spend working at some other time.