Cuase they have money, and or time to spend, and nothing better to spend it on? So when they take their pc to a lan party someone doesn't say 'WTF has a family of rats been living in your case?'. Someone once used the reason I like seeing all the parts moving around inside, answering the question of why did he replace the harddrive cover with lexan. You have to ask each individual person, because everyone has their own reason. My reason when I used to mod my case was performance, and taking a sawsall to the side panel sounds like a good idea after half a bottle of vodka.