Well the reason you can get sued or prosecuted for setting up traps isn't to protect criminals, it is to keep people from taking the law into their own hands. True enough a couple flat tires would certainly be a nice lesson for them, but how would you feel if it was a couple kids riding those wheelers and when those tires blew out they rolled the wheeler and got paralyzed or killed? Certainly they would be in the wrong for trespassing, but would the punishment fit the crime? Or instead of kids it was a couple real bad guys, and instead of a couple blown tires teaching them a lesson about trespassing it incites them to turn it up a notch, and the next thing you know your tires are slashed and your windows are broken or worse. I'm sure you can imagine lots of other circumstances where something could go wrong or things get out of hand. So when you think about it, the idea isn't really to protect criminals, it is to prevent vigilantism.