Benny's bad grammar

Has anybody else noticed that Benny often uses bad grammar in this film. "Now we can't play no more" and "We gotta buy us a ball" are two examples. I wonder if this was an artistic choice on the part of the filmmakers. I've noticed that works of fiction, especially ones set in the past, do this to make a character seem low class (because they don't have much education). Do you think that was the case with Benny? In this setting, school was easily available but he could have had relatives who didn't have much education (possibly immigrants from Mexico) that affected his speech. Or it could have been meant to make him sound casual or something. Or it could have meant nothing.

What do you think?