USB mass storage players also fail nicely at being usable for most normal people. Plug it in, get an Explorer window, now what? Open another Explorer window -- reposition windows so you can see both. Navigate to your music collection. Find the first thing you want to copy -- hopefully your music folder is well organized by filename. Copy (don't move!) files. Make sure there are no incompatible filenames. FAT32 isn't very forgiving about this. When you're done make sure you safely unmount the volume by right clicking on the green arrow in your system tray (the thing by the clock). If you have multiple green arrows just try right clicking on them all until you find the right one. Now enjoy your music and start preparing to repeat the process tomorrow when you want to add a song.
At least you have the option, and the device doesn't go out of its way to make life difficult for you and any software that tries to access it.
People love to think that users are completely clueless, but it's not the case. The general user has absolutely no problem using a USB drive. Sure, it might not the most usable option but it's not as arduous as you describe.
And organised music folders? Either it matters, and you play music directly with Winamp (or similar), or it doesn't matter at all and you use a jukebox program that works with the tags. You can also just play music straight off the drive if you want - fairly common in my experience.
I've been using iTunes since version 3, and I don't think I've ever seen it treat a mass-storage player like an iPod. There was, however, until perhaps very recently, vestigial support for a handful of very dated mass-storage players, a strangely-untouched holdover from SoundJam MP. I never did see what would happen when one of those was plugged in.
There is nothing intrinsic about USB mass storage in that experience.You can make an iTunes like experience based on USB mass storage drivers, Apple has chosen not to for other reasons.
