Good thread. Fully agree for single tickets, with a large DD savings baked in, and for someone not at the airport it makes little sense.

But as others have said the DD discount is often much less than $10, especially on super cheap fares. I fly with my wife + 3 kids a few times per year for leisure travel. I'm already seeking out cheap tickets since I'm buying five. In those cases I've been twice able to stack buying five tickets while I'm already passing through the airport flying solo. At $200/trip savings it's an easy move in those instances...the line sucks but I'm usually catching up on work email anyways so it's semi-productive.

But, to your original point, when I'm buying tickets for just me I rarely buy them at the counter.