Even though going to a training camp session is free, the whole point of the public part of camp is $. That's why they herd you through the vendor area and merchandise tent on your way to and from the field. They want you buying gear & food. They want you connecting personally with the team so that you'll buy tickets. They want you to bring your kids so that the next generation of fandom is on board.
Not sure how much of that happens if you're watching it on TV.