Yes partly alcohol, but also the front of the house is cheap to run. In the old, old days you only had to pay waiters $2.13/hour and they made the rest off of tips. Now it's like $8/hour in our state (Colorado) but that's still nothing, when you consider how many tables (and entrees per table) a single waiter can take during a busy hour, far less than 20% of each entree for sure. The problem is demographics are changing. Our restaurant 20 years ago did like 10-20% takeout and delivery, the rest was all dine in. Now it's closer to 50-60% takeout and delivery for us, so companies like GrubHub are eating up a lot of restaurant profits. People just don't eat out like they used too. It's not just us, there have been a ton of articles the last couple of years complaining about these companies, this first one says GrubHub takes 30% (yikes):

https://www.chicagobusiness.com/joe-cahill-business/restaura...

https://www.newyorker.com/culture/annals-of-gastronomy/are-d...

When I mentioned GrubHub and DoorDash to my wife when I say this article posted, I got a 30 minute rant about how much she hates them. She couldn't even give me a fixed fee she paid from these companies, she started listing off different fees and charges, but she said it was more than 20% per order. These companies have absolutely shot themselves in the foot with how they have treated their customers. What a lot of people really want is to be able to order online or through an app, that's the value these companies provide. For us we already had a WordPress website, so I paid a small fee to install the Woo Restaurant plugin to handle the online menu and ordering. It really wasn't much trouble to setup and it's been way less trouble than any of these middle men, and we get to continue to keep the profits.