For no specific reason, in most cases, features such as dual LAN and other 'extra' features are included in later releases.
What exactly is a "later release"? Do you mean the "X.1" versions of the boards? That would be really nice.
Re the first answer:
Well could you give me any technical reason (think logically
why a sound output jack would depend on the chipset or the CPU? They are completely unrelated, as we don't have sound in the chipset nor the CPU (yet). There are additional audio controllers (aka codecs) for that purpose. So this must be a part of Gigabyte's strategy, I think.
BTW, I don't own an AMD nor Gigabyte board at the moment. I was exactly doing what you had proposed there - researching the available options
and doing so, I've come to a (seemingly silly) limitation. So I want to find out the reason for it.