I regularly fly all over the world, and it's nice to know how long my flights are going to be? I'm not always flying direct, and seeing the lengths of the legs and the lengths of the layovers allows me to plan my day and my sleep schedule.
You do have landing time for all of the legs? That’s more useful than duration. For your sleep, you care about landing says, at midnight, as oppose to a 10 hr flight from Paris that may or may not arrive during day time at the destination.
No, duration is far more useful than landing time when my basic desire is to know how long I’m going to be on the plane. A 2h flight vs a 6h flight is a huge difference in experience. Also, landing time is given in the destination timezone, which does me no good. The part of the day that it lands is basically irrelevant to me.