Because you never know what trivial bit of information may ultimately prove to be vitally important.
I never made the connection with a particular ethnicity, but I have seen the stickers on cars and such all over town. At first, I thought it was something related to a car club, perhaps an inside clue for swingers or cross-dressers, and I even speculated about gang affiliation though admittedly, it wouldn't be a very intimidating logo. In the end, I guess I've never bothered to research it. Betty Boop gives me the creeps.
I can say I'd noticed any affinity for that by any group in my particular corner of Texas, and I'll admit that I live in a very "ethnic" neighborhood, with Mexicans on one side, blacks on the other, with an occasional Vietnamese sprinkled her or there. I do remember back in school, that the police gang taskforce would compile a pamphlet of gang-affiliated clothing and send it out to the schools, where the principals would then tell the students they couldn't wear this or that, based on last year's list. Anything with the Oakland Raiders was verbotten, along with the Bugs Bunny and Mickey Mouse cartoon shirts that were popular then (supposedly the initials "MM" on the Mickey shirts could substitute for "mean Mexican"). I can see where schools would end up going to uniforms, just to keep that junk out, even tho I think it's inane.
I agree with Dave. I shudder a bit every time I see Betty Boop.