Also they are timed as to how long their customers sit in drive-thru. You should not sit at the window more then 120 seconds.
Because as a previous fast food worker the thing is if the drive-thru needs to be taken care of quickly. the meaning of fast food means getting your food out quickly and accurately as possible. Dine-in customers do get served but they're not as much of a priority as the drive-thru. When you're in the Drive-Thru you want to get there and get your food and get out and get on your way as fast as possible but when you're there to eat in you're not there to do it quickly
The philosophy is if you're willing to get out of your car your are willing to wait a few minutes for your food.
Thanks! Your answer is awaiting moderation.