Might be because I was specifically ordering from places that _weren't_ downtown. Like many others on the thread, I don't particularly care for the delivery services so I really only use them to grab things where it's infeasible for me to go get them myself. With public transit, getting food downtown was easy so I was ordering from places out to the east.

I'd guess rain. There's only a few dry summer months.

Seattle ain't the only place in the world it rains a fair bit! And I gather it's rarely particularly heavy rain.

They probably already have a car.

I'm sure plenty of food delivery drivers have cars here too, but the cost/ parking/traffic issues involved in using one for such deliveries in a higher density metropolis make them kind of impractical...