From my understanding, the modern species of honey bees radiated out of
Central Africa/Middle east and have all evolved separately from that point.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-294X.1992.tb00170.x

What's important about this ancestry is that the common ancestor to all
honey bees today was a primarily cavity/rock crevice dwelling species.
Thus, we can deduce that a great fraction of the traits that modern honey
bees exhibit evolved in species that dwelled in caverns/crevices
primarily.

  At some point in their evolution from wasps, bees decided that cavities
were preferable over open air colonies.  The reason for this is
multifactorial.

What may explain the fact that some species of honey bees do not dwell in
cavities, is the fact that one a trait evolves, it is not immediately lost,
so long as it does not directly impede survival.  Generally speaking, it's
easier for a species to modify their *behavior *rather than "de-evolve"
some feature of their physical biology.

Thus, perhaps the Asian Honey bee, which builds its nests on limbs of
trees, can still manage to survive heavy downpours. The capped wax
obviously repels the water, and does not need to be covered, so the bees
can focus their attention on covering the brood from the rain, while still
retaining stored energy in the capped waterproof honey.

-Alex

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