You're stil going to get to the same place at the same time as the other passengers.
True, but you have a nicer seat with more room, and everything before and after the flight runs faster and smoother. You have your own check-in desk and security line, so you can arrive at the airport an hour later than the economy-class passengers. You have a bigger baggage allowance, so you might not have to put anything in the hold - and if you do, it'll probably come off the plane first. All that can make the difference between a day trip and an overnight stay, or turn a trip of n days into n-1 days.