Tables 300.5 and 300.50

[mshields]

Both of these tables for burial depth of conduit have varying values for direct buried conduit vs conduit in trench "beneath 2 inch thick concrete". I suppose that includes in a duct bank provided that the concrete on the top of the conduits is 2 inches thick - do you agree? But why, when most of us either go direct buried or encased in a duct bank, does the code make it sound like putting in a slab above direct buried conduit is the norm and not mention at all, the use of duct banks.

I realize the question is speculative but if you have any insights they would be appreciated.