I've never programmed to Mac, but looking it up revealed that there are dynamically loaded libraries in Mac (even if they're not DLL files).
So I assume it's mainly because Aspyr didn't want to put the extra resources for this (it wasn't in the contract, or they don't really care about the community, or both).
It could also be a result of Apple's restrictions
I'll believe anything on this company.
As William said, both are not supported by the current code and require extra coding.
The emancipation idea is quite good, but I'd rather have 1 UC for each civ, I guess.