The promise of a set fare is a big draw, I certainly like that I can quickly compare fares from Uber and Lyft and choose the cheapest and know exactly what I'm paying. Also the fairly accurate arrival times are useful especially when I'm planning trips to the airport, knowing when I need to leave the get there on time. Also the "card reader" is always working on TNCs and I have confidence that if something went wrong during the journey the company would quickly refund. Also I love the shared ride functionality in TNC apps, makes me feel a little less bad about not taking transit. And makes them cheaper usually. Oh and lastly Lyft gives you Delta skymiles for airport journeys which is a nice bonus.
I always thought there should be a flat rate out of Logan like NYC. As for the card reader - if its out just say you won't pay and even offer to call the police if they make a fuss - its amazing how quickly it magically starts working again. That said, I haven't had a cabby pull the broken credit card machine in years.