It's true. The government says so. In fact, that's why you can't get a real trial. To quote: "You have been cited for a violation, not a crime... Since this is not a crime, you do not have the right to jury trial."
If it's not a crime, then what is it? Oh, a "violation". A violation of what? The law, right? Is that not the very definition of a crime?!
Does not the seventh amendment to the US Constitution say:
In suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise reexamined in any court of the United States, than according to the rules of the common law.
This whole thing smacks of semantic gymnastics to make it impossible to get a trial by one's peers, as that would make their revenue-collecting machine much less efficient. They even try to discourage you from fighting tickets you didn't deserve. However, they make it extremely easy to just pay the fine.
Upon further research, it turns out that this is called the "infraction" system, or the system of "civil sanctions". The government's rationale (which I don't agree with) is that since you cannot be incarcerated as punishment for an "infraction", they're allowed to deny you the constitutionally-guaranteed protection of the jury trial, and they presume guilt, so you have to prove your own innocence. But since you can still go to jail for not paying the fine, say, there's nothing to stop them from slapping you with an unpayable fine and then just taking you to jail when you can't pay it. Or when you don't pay because you were actually innocent.