Yeah, why does stuff normally suck? You have these entities with decades of experience in producing stuff (or waging war, governing people, etc), and they're not so great at what they do.
An OS is typically a boring abstraction layer. A car is a personal transportation device. The people working for these companies are mostly wage-slaves going about their tasks, for people who want to make money. Why should these things be eye-poppingly exciting... for more than a few years? At least as far as most people are concerned?
That said, I tried out a preinstalled Windows Vista on a machine (before I wiped it). Looked fine to me. I don't think it's particularly shoddy. It's just uninteresting.
Tayssir