Just read this short article on Powder's website.
To me, how a ski area treats sack-lunchers is a very good indication of how much I will like a ski area. Even in cases where I'm not bringing a lunch.
In my eyes, in this day and age, if a ski area is willing to give sack lunchers a nice place to eat, it means they want to earn my money rather than dictate that I spend it. They want to earn my business by making their food so much better than the ragged PB&J living in my boot bag that I decide to buy lunch, rather than coerce me into eating their overpriced food.
To me, the difference in attitude shows up all over the mountain- a mountain willing to give up profit by allowing sack lunches is a mountain that is concerned over how the negative experience of being forced to buy a lunch is going to detract from the skiers experience, and generally will take other steps to make the ski experience friendly to day skiers. They are more likely to care about stuff like minimizing walking distance from the parking lots to lifts, speeding up action at the ticket window, making sure deals exist that will get you back to the mountain.
A resort that has already taken the step of forcing you to buy a lunch from them if you wish to sit indoors is also looking at all the other ways to extract the maximum amount of money from you. It's not "How can we make their day better?" It's "How much will they put up with before we lose them?"
Refusing bag lunches is a step down the path of pay parking, building condos on former parking lots, forcing long hikes through base villages to the lifts, opening the lifts early for those that pay more than you or stay in one of the condos you had to hike past, adding private lift lines, etc. etc. etc.