Interesting article on the history of USB over on IBM’s site.
USB, even after support for it was available in Windows, faced an adoption problem. Standard adoption is largely driven by network effects; the utility of a standard-compatible device comes from its ability to interoperate with other things compatible with the same standard. A standard is only useful to you if there are compatible devices and if there are a lot of them.
This creates a Catch-22 situation for adoption. If users lack USB ports or drivers, those users cannot buy a USB device. For vendors, that limits the market for USB devices and makes it more reasonable to develop peripherals for other ports (such as the once-ubiquitous serial and parallel ports, or the SCSI port if you also wanted to tap the Mac market).
Even if users would prefer a USB device, they would still be more willing to accept a non-USB device since it can be connected to their computer. Even if USB is a better, more desirable piece of technology, it may not be more marketable than the alternatives! The number of people who would buy a USB Webcam might be smaller than the number who would buy a serial Webcam — and almost all of them could be persuaded to buy a serial one instead.
It also talks a little about why USB sucked on Windows 95, and notes how Apple finally gave USB the break it needed to take over the peripherals market.
I also got a kick out the the little author bio at the end of the article (emphasis mine):
Peter Seebach is a standards enthusiast who has been using USB devices for years.
When you’re described as a ‘standards enthusiast’, you have entered the hallowed realm of the alpha nerd. I’m just imagining posters and t-shirts with USB logos on them.