Fast food, overall, isn't particularly fast anymore. There are some exceptions of course. However, for the most part, especially when going through the "drive-thru," if there's two or more vehicles in front of me, I usually find myself experiencing quite a bit of wait time. If I pull into a fast food restaurant lot and see any amount of traffic backed up in the "drive-thru," I will just park and go inside because, more often than not, the inside of the restaurant will range from anywhere between completely empty to one or two people in line, and the lines inside always move so much faster than the drive-thru does. The drive-thru forces employees to work on and focus on one order at a time, whereas ordering inside will get your order in much more quickly, increasing how soon it is worked and focused on.
I realize that the temptation to stay in one's vehicle can be strong because it requires less effort, but if I see a line in the drive-thru, I won't hesitate to park and go inside. Additionally, if both the drive-thru and the inside of the restaurant are both packed with people, by going inside, I have the option to bail and go somewhere else if I discover that service is painfully slow. If I had gone into the drive-thru, I would have found myself trapped in line, with no option but to wait it out.
I really don't understand how anyone becomes a fast food chain or franchise owner and then fails to make speed and customer service their top priorities. And as some of you already mentioned, many of these place that I've been to are blatantly understaffed and highly disorganized.
Sorry, I'll stop talking (typing) now. I forgot what my point was! =-D