The Brother-in-law

Ok, so first thing is first....
so, Hubs has a brother, R. His brother has a partner, C. They have been together for 18 months. Sometimes R does things that get under my skin. Our family dinner this weekend was one of those moments. The whole family met at a large chain steak restaurant for dinner to celebrate R and C's birthdays. Their birthdays happen to be over the next two weeks and this was the only weekend we could all get together. Before I go any further, you should also know that the in-laws do not drink any alcoholic drinks, so when we go to dinner with them, there is never anything ordered. On the few occasions that I have wanted a drink at a family dinner, I have excused myself, gone to the bar, gotten said drink, paid for said drink and then returned to the table. That way the drink never shows up on the bill. We always split the dinner bill. The way Hubs and I handle it on our birthdays is that the non-birthday person gives the money towards the bill. We have been handling it this way for almost 13 years.
Back to the dinner, they were almost 20 minutes late to arriving at the restaurant, so we had already been seated, looked at the menu and ordered our drinks. When they arrived, they sat down at the table and the waitress asked if they wanted something to drink, one ordered a coke and the other a gin and tonic. Ok, so that drink was almost $9. My jaw dropped as the waitress brought it back to the table. It dropped a little bit more when drinks 2, 3 and 4 arrived at the table. While we waited for dinner to arrive, the kids entertained everyone with jokes, a history lesson and taking pictures on their DSi.
Dinner arrived and I really enjoyed my steak. It was yummy. We skipped dessert at the restaurant in favor of returning to R and C's condo for yummy mother-in-law made cupcakes. So the waitress brings the check. She hands it to hubs and he looks at it, decided how much money to give towards it and slips the money inside. He then hands to his brother, who passed it right to their father and announces at dinner that they would not be putting money in tonight as we where out to celebrate their birthdays. Plus in addition to the drinks they also had two of the largest most expensive dinners on the menu.
My in-laws took the bill and covered the extra without saying a word at dinner. When we left the restaurant, the kids decided to ride with the in-laws to the condo, Hubs and I got in the car and talked about the bill. See while we where sitting at the table, I did not look at the bill, it was only afterwards did hubs tell me that each drink was $9. He was mad that they stuck his parents with almost $40 worth of alcoholic drinks.
So my question to ya'll is... when you go out with family would you order alcoholic drinks if no one else at the table is drinking? Would you stick someone else with your bill?