I think the answer might be that the lowest large portion of their society—aside from some marginalized groups and outliers, talking the broad base of their soc

I think the answer might be that the lowest large portion of their society—aside from some marginalized groups and outliers, talking the broad base of their social pyramid—is their working class, not something else even lower. There's enough affinity or in-group feeling among the working class that it's not divided into a whole bunch of categories, with some very low ones indeed that are very clearly and visibly way under the top of that stratum, but into a smaller set that still consider each other fairly similar and "one of us", for where-am-I-on-the-social-hierarchy purposes. (pure speculation)