Here's something for you to think about. The reason surround sound works is because of the distance between you and the speaker in the right locations gives you that since of direction, the spacing helps you determine the direction.
When using 7.1 surround sounds, in order for them to fit the drivers in the headsets, they have to use smaller speakers, thus you lose audio quality. Surround sound mode? Well...you don't have speakers in front of you, you dont' have speakers behind you, all the speakers are right on top of your ears so you really dont' get a sense of direction. I have a pair of surround sound headsets and I thought they were amazing even though the audio quality was crap. I was told I could get the same effect with a really good pair of stereo headphones. So I got my Sennheisers 280 pro. The audio positioning is the EXACT same thing.
Why do they sell? Marketing. People fall for marketing and that's what the people in those positions get paid to do. Sell crap. It all sounds so great on paper doesn't it? Who wouldn't want a piece of it! Unfortunately some people don't research into something before buying it, they just think it sounds great, and when they get it in the mail, of course it's going to sound awesome because they just spent a crap ton of money on garbage so they make themselves think it's amazing.