Welcome to AT Network forum.
To put it in perspective, in the last year many new Mobos come with additional NICs, as a result people get excited and thing that they can Squeeze more from their newly acquired system.
If you are using a regular computer with Windows Client OS there is No Bandwidth/Load (?Speed?) advantage in using more than one an NIC.
If you have, special needs you would need to invest in special hardware and use server OS to benefit from additional NICs.
:sun: