It's only when in US, that if you witness or are a victim of robbery, that all of a sudden, you want a U-visa.
First of all, if you're a tourist, how'd you even know about it?
Second, if you get robbed, isn't your first priority to move on or leave the country? Tourists get robbed in other parts of the world too. Do they then ask the host nation for a visa? The True Geezer (the dude who's curently on the news for running the whole length of Africa), or whatever his name is, was robbed in Angola in one of the legs of the races. Did he demand any certain visa from Angolan government?
How'd you even know the person that robbed you was a USC or even legal??
Citizens of those countries also get robbed. Should they demand free rent from the government for a while year since they don't qualify for visas?
One lady witnessed a crime and was asking if it qualifies her for U-visa. Another's illegal father was working at a job (illegally) and was punched by a coworker. She's asking for U-visa.
My conlusion is that most non-immigrants come to US with sense of entitlement. They're also coached.