I looked this up and apparently, taking the to-go box is less common in Europe. I might be able to justify it there -- the restaurants there are much more likely to provide the appropriate sized portions rather than American-style "all you and your family can eat in between two buns" portion.
That's true, was one of cultural oddities I encountered when I moved to US. However usually portions offered here are not so large that it would be an issue. There is a funny relationship though between a price of a restaurant and portion sizes. Generally speaking in fancier places portion sizes are smaller because they are hoping you'll also take appetisers and a desert to feel full. In standard price places I can only eat an entree or salad+desert not all of them. I'm a big guy but not a big eater.
Talking about antimustachian I was earlier this year in the fanciest restaurant in my life. Food was fantastic (4 courses plus wine), but the bill was fantastic as well (ca 120$ per person)…