To use your water analogy though, I would see the equivalent to what I was proposing as the government providing clean water through your taps. Want to drink it? Go ahead. Want dirty water? Go to a lake. Want to buy water? You can do that too. Options. But, by the presence of the clean water they're encouraged to use it over lake water should they want a drink of water. Don't want to wear a helmet, okay. Go ahead. But through the presence of a law (even if it isn't enforced), you're encouraged to wear one. It's suggesting, not forcing. It's against the law here to drive without wearing a seat belt, but I'm not being forced to wear it. I can pull out of my driveway without it and likely no one will know. I have that freedom. But the threat or risk of a potential ticket encourages me to wear my seat belt (along with other better reasons).
To use your analogy.. it would be like "You want clean water? Go ahead, we're giving it you. You want dirty water? Pay us money and we will let you drink it. But NOT ONLY THAT, we are going to take time out of your day, "pulling you over" to let you know that you owe us money because you didn't drink OUR water. And from that... in a couple of days you are going to have to give a visit in court where you can appeal to not pay us... but our trained professionals know best so we're just going to make you do it anyway.