Groups in Restaurants – whats up with the rule that 6 people or more can’t have their bill split?

I met up with friends and workers for the camp last night at a local bar for a drink and dinner.  We have done this dozens of time.  Last night when our group of 17 (8 couples plus 1) or so was done the waiter tossed the entire check on the table. I have to mention that my partner worked in food service for years, so we have a reputation as generous tippers with nearly every place we frequent. When I said, "hey" we needed this separated, the waiter said, "we don't do that for groups of over six people.!"  He then disappeared, as if he had just tossed a grenade. This had never happened before so I was taken by surprise.  I had drank a couple beers and a shot, so I wasn't shy.  I said, loudly "That's not going to work for us." This resulted in an unpleasant exchange, which did little to aid digestion.  We each had to split up and cower over the waiter station to sort the bill out and pay individually. Tell me what is the possible justification for a policy like this? Yes we were 17 people, but what is the difference if we came in and sat at different tables?  From the owners standpoint, we are 17 meals and drinks - what difference it is what configuration that we sit in?  I would think that psychologically having people pay individually  should result in higher tips overall.  Everyone has paid in a group only to discover which of their friends are crappy tippers.  The cheapskates really seems to come to life when they are paying undercover as part of a group. I have to say my group of 17 to 25 people that rotates between local restaurants is not likely to return to an establishment with a policy like this. In an age where computers run everything, a sharp waiter could have made fast work of keeping track of the couples and dividing up the bill - I have seen it done dozens of times.