they didnt just "dip into it"?? it was a main focus for much of blakes backstory in v2 & v3, there was an entire whitefang arc in v4 with blake & sun in Menagerie, it was continuously brought up throughout v4/v5/v6, in v7 is was again shown how unequal & how discriminatory every one is with the miners in SDC mines, the segregation of the fanus living in the crator which is even lower than the poorer people of mantle, in v8 the segregation is STILL brought up bc they're still in Atlas, its even shown that the fanus are letting the people of mantle come to the crater for saftey despite the people not liking it (ex- the old lady complaining), its also shown the discrimination has been around for a long time because its shown in the cinder backstory episode, Ilias backstory in v4, and the v6 episode with Jinn and Salems backstory. Its been nothing but relavent the entire show. Its not the main plot but its not like they did 3 episodes on it and forgot about it. The way i see it is they're using it to show how divided humanity is and how hard it will be to bring everyone together for the gods judgement day that Ozpin has to prepare for. Racial issues run deep.