There's a qualitative difference between "pay" and "no-pay", particularly among students with no income.
When I was in college, I had essentially no cash flow. Nothing in, nothing out. The college dining hall was open 7 days/week, so I always ate there instead of eating out or cooking. (The only times I ate out were the TYPO - "Take Your Professor Out" - dinners, which the school paid for.) Room & board was completely paid for, and we weren't allowed to live off-campus. Internet access was provided by the college, as was webhosting. Student activities (I did sailing, orchestra, taiko, some artsy-crafty stuff, and a variety of other things that would've otherwise been expensive) all came out of the student activities fund, which was paid with our tuition. I bought books once a semester with a credit card that went to my parent's account. After the first year, I didn't bother signing up for a room phone, instead using my cell phone, again paid for by my parents. The only thing I ended up paying for was ordering Wingz or pizza at midnight, or alcohol contributions to parties.
There were many purchases that I could easily have afforded that I didn't bother with, because it meant I would've had to worry about money. They included Starbucks, going out for meals or ice cream, paid LiveJournal accounts, actually buying music, and basically anything that required a credit card (I didn't have my own until I got a job after college). If GitHub had existed back then and charged, I would've said "Screw it, I'll setup my own git account on a college server, and we can all pull from that."
The cost isn't just $7-12/month. It's all the time spent balancing bank statements or checking over credit card bills that you wouldn't otherwise need to worry about if you never use money.