It's like a Ricer, the looks are literally just as important as the power. If it's not it's considered a "sleeper" with cars. You just can't pull off a sleeper with PC's, if it doesn't look good but runs good, that can mean anything from you're ignorant and bought it pre-built for $4000, or you're a nerd that renders 3d things, or you're just a lazy gamer, or you don't have a passion for computers. See? Without mods you're any of those, but with mods you're either an ignorant computer builder that loves looks and nothing else, or you're a dedicated enthusiast that loves his works and shows it with how his case looks.
Sleepers just mean you're lazy or you don't want to brag, or you're a hussler. How are you gonna hussle with a computer? Ricers can mean exactly what a modded computer means.
See the difference? You can't pull off an ugly computer like you can a car, it just shows your passion for the hobby and it's even more important with computers.