I dislike the idea, but, it shows up in other areas. Electricity being one. Another might be gas and oil, instead of time of day, it's time of season. By messing with pricing, they can try to shift demand around--or at the very least increase money so as to pay for the workforce when they have to upstaff during certain hours. And/or pay for staffing during off hours.
Personally I prefer to swing into a grocery store and peruse their shelves instead. I can't always grab stuff from home when out and about, but I long ago lost the taste for fast food, and have no love for sit down places anymore. Will admit to still ordering in, once or twice a month, but am reluctant to pay for any more than that.
But some have to eat on the go, and are not home bound like I am. Sorry for you guys, yet another complication in life.