The coolest case I’ve ever seen was a tower (not a mini-tower–lots of bays!) made of brushed steel with a “door” of green-tinted glass. VERY sleek. (Plus it had some USB ports in the front, and a temp gauge.) If I ever build my own machine, that’s the case I want.
I think more manufacturers are focusing on the looks now because PCs are ubiquitous. They’re not just for geeks anymore. I, personally, spend a lot of time in my computer room, and I would like that time to be an all-around pleasant experience. (No, two of the PCs in my computer room haven’t had open cases for weeks. You must be thinking of some other skeptic_ev.) Aesthetics is a big part of it. I could throw a sheet of plywood on two sawhorses and use it as a fully functional dining table if I wanted, but would I? Not unless I had to.
OTOH, I don’t really care that much about what my car looks like.