Surround sound, actual human ears, how we perceive sound operates off of volume and delay. 5.1/7.1 is still wired in stereo with a left channel, right channel and a ground. USB headphones have their own DAC/amp and maybe also VIRTUAL surround sound. Virtual surround sound and ACTUAL headphones are best for the most immersive surround experience.
You're paying a bit of a premium for the title 'Gaming' along with extra drivers that you DO NOT need. Talking to you Astro.. five drivers in one ear doesn't do anything.