We're in a transitional period. The vast majority of people who have iPads
do have a PC of some kind also. For now it's the most practical way of doing backups, updates, and syncing large amounts of content. I do think Apple will move in the direction of not requiring a PC for these things but it's non-trival. How do you sync 16-64GB of data over 3G? Do you push 300MB+ updates to someone with a 150MB/month data cap? 2GB? How, and where, do you sync purchased content? How do you backup the device? This is a very important feature iTunes provides that most people won't even notice until they have some need to restore a device.
The newest iOS update has modified the way OS updates work by not erasing/re-syncing the device. I suspect this is one of the first steps towards moving to a more OTA existence for the iPad. They still need to trim down these updates so they're not killing people's caps. Everything on the content side is going to require a lot more work. If you look at Android for example that does just about everything OTA you realize that a) Google doesn't really sell content so they don't care how or if you get anything on your device. Figure it out yourself. b) Android doesn't backup automatically. Some of your data is synced to Google Services but if you flush your Android phone down the toilet by mistake you're going to lose all your application data and content you synced, or created, on the device. Again -- figure it out yourself if you want a good backup c) Google doesn't update all their devices at the same time. There will never be 100 million+ Android devices trying to download android3.0.tar.gz at the same time. It's a bigger challenge for Apple to do OTA updates given their strategy to update all compatible iOS devices at the same time. I'm not trying to bash Google, their system is fine, but people make it sound like this super trivial thing to divorce post-PC devices from the PC. It's not. Google has been able to do this through minimalism. They don't take any responsibility for updates/backups/syncing so it's a bit easier for them to pull this off right now. If you use Google Exchange with an iOS device you get most of the same benefits in-fact.
Apple could easily divorce the activation-via-PC step but it would set the expectation that you don't need to connect it to a PC ever for normal operation/update/syncing. When they do remove the activation-via-PC step you can be sure everything else won't require a PC connection. It will be all or nothing. That's how Apple tends to operate.