I really can't come up with a real reason for them to be so slow, either. My friend and I had a good view of both the lobby and the kitchen from the drive-through. Only one person came and went in the lobby during our time in line. There were two cooks plus an order-taker inside. The drive-through curved, too, so we could see there weren't a ton of people in the cars ahead of us and the bags we saw handed out were relatively small. Even if there were, we didn't order much food and it still took a long time for us.
To top it off, this was the type of drive-through with a median on either side, so we couldn't even pull out of line to go somewhere else. ...Okay, technically we could have because I have a lifted jeep and it laughs at medians, but I'm not into property destruction.
Seriously, if anybody in the fast food industry can give a reasonable explanation, that would be great. If not, I will feel content in my gripe.