People are willing to put a couple of weekends into making a middle school or high school competition happen. They're a lot less willing to do it if they have to go to an FBI station to get fingerprinted or produce a state and federal background check first. And I'm not talking about people with something to hide; I'm talking about people with a completely clean background who just don't want to be bothered.
Few years back got chased by a cop and ticketed (and scolded) for not restraining kiddo (small town and my clever 2yo somehow learned how to unbuckle themselves (even that houdini clip didn't help)). Warned I could get prosecuted for child neglect if I continue. I suspect the daycare has tipped him off.
2. Supposing I did believe it and did say it, I would be well within my rights to say it. The First Ammendment assures the right to say things like that, no matter how dumb and misguided those things are.
But for many DUI checkpoints safety is not the goal. It's simply a pretext to check everyone's papers.
Or is perhaps the chance of a random test at any moment more of a deterrent?