[alistairSH]

Yep, Dulles opened just as jet bridges became common. They were originally used for embarkation/disembarkation as well.

These days, they're mostly used to transport international arrivals from the gates (which have jet bridges) to the terminal that contains immigration control. Non-international have an option to use the lounges or a subway (usually depending on which gate you're at and where you need to go - sometime the lounge is faster than the train).

A bit of an anachronism today. But, having grown up in the DC area, they're definitely have a nostalgia factor.