In some societies, we observe a seeming paradox: a bottom social class refusing to assimilate, refusing to give up the social markers that identify them as part of the bottom class, markers by which they then get discriminated. Possible explanations:
The paradox is an illusion. We only notice the few unusual outliers of those refusing to assimilate.
Assimilation takes generations due to the time constant of psychological identity.
Maintaining the social markers buys into a social safety net within the community of that class, which is more valuable than the risky benefits of assimilation. They are making a rational decision.
The opportunities for assimilation are actually illusions. No amount of dropping social markers will disconnect you from your social class, because the upper classes want to keep the lower classes well populated.