T-Mobile charges $ 60 per month for a single mobile phone line with 3 GB of LTE data. The same service is $ 20 per month per line on a 6-line family plan (2.5 GB LTE data per line). Why then are there individual phone subscribers? Assume six single people who happen to be at least casual friends and all of whom want to use the same carrier. Why wouldn’t they form a family of 6 and then cooperate to pay the joint bill?