And real estate costs.

This is probably the answer, combined with the continuing cost of building new restaurants in expanding suburbs.

I'm wondering if franchising has something to do with this. There are just so many fast food restaurants along the highways and dotted around the sprawl of big box stores that surround towns these days. And they seem to always be nearly empty.

My (wild) guess is that some of this is that the motherships are permitting overbuilding. They get their franchising fees regardless, and don't necessarily have a whole lot of reason to care if their franchisees are bringing in enough business to turn a healthy profit.

Isn’t this part of what put Krispy Kreme into bankruptcy?

Exploding health insurance costs for all employees that qualify are also being passed on to customers.

How many employees in the restaurant industry get health insurance? There are many millions of waiters, cooks, busboys, greeters, etc... that get paid minimum wage with no benefits.

Not really an issue in the restaurant business.