Some people have a strict preference in the manufacturer they buy from. Lots of people were EVGA fans and only bought from them, it was nice to see reviews on some of their available cards when things got released. Same goes for all other brands.
I was a big fan of Zotac for a while. Had a stellar GTX 570 and I was pleasantly surprised with the 980Ti AMP! Omega from them as well. However, they started having build issues the following series with the 10x0 cards and kind of kept going down. It was nice to see reviews on their stuff and hear about any issues so I could make an informed decision where I to buy another GPU from them or not. I'm not against buying from Zotac again, but I would like to be informed before I just drop money on a GPU.
Also, seeing a lot of reviews lets you see what these cards look like, sound like, how they handle temps and if there are any oddities that stand out (good or bad).
Not only that... but... its completely possible to have a rig you don't really notice while gaming. Always having cans on... I never understood that. It annoys the F out of me after 10 whole minutes already. Even outside. No matter what headset it is.
I love playing games with headphones off at home, but I can rarely do that because someone is always home and they don't want to hear what I'm listening to come out of the speakers. I can't stand things in my ears aside from eat plugs I wear at work when needed. Earbuds hurt my ears and constantly wearing headphones in a non-temperature controlled environment (like my home) can easily cause me to start sweating if it got too hot. I'm not for wearing headphones when it's hot and sweating all over them - gross.