Like I said,
I don't know the political/contract structure between Apple and AT&T/Verizon. As much clout and pull as Apple (and the general public) think they have, they don't own the towers and the cell network. AT&T, and Verizon in particular were doing just fine before Apple dropped a phone in their laps.
For all I know the carriers put a clause in the contract that prohibited Apple from publishing tethering apps since it was a conflict of interest with the tethering plans they would rather push on subscribers. Apple needs the carriers more than the carriers need Apple so the likely have to comply.
I don't think it's a restriction call made by Apple. I think they are simply bowing to the phone companies wishes. It's a a tricky relationship.
The carriers are trying to go after the Droid Market place too....
http://www.androidcentral.com/verizon-and-att-blocking-tethering-apps-android-market
Fortunately Droid users do appear to have a way around that, for now. If the carriers feel like it's abused enough they'll start packet sniffing on suspicious accounts and handing out nastygrams just like they did to iPhone users.
EDIT: actually they are already...
http://phandroid.com/2011/05/31/verizon-cracking-down-on-users-illegally-tethering-on-their-network/
I doubt Google's lawyers and negotiators are any better than Apple's.
Google also doesn't own the towers or cell network. AT&T and Verizon were also doing fine before Google dropped Android on their laps.
When you upload a software as a developer on Apple's App Store, Apple is the publisher.
This is no different from Google's Android Market. You are the developer, Google is the publisher.
Google needs the carriers more than the carriers needs Google also.
Why would the carriers make such a demand on Apple and not do the same to Google? It would be stupid of them not to do so. I seriously doubt that Google somehow negotiated a superior agreement to Apple.
More than anything it's probably Apple themselves that just doesn't want tethering on iOS, period.
I know you personally can't answer my question since neither of us knows what's in the specific contracts.
I seriously doubt that Google negotiated a more superior contract than Apple did. If they did and that explains why there are tethering apps on Android Market, then I say good for them.
Like I said before, You can turn off the cell towers in Android, enable WiFi and download the tethering apps you need if your carrier is blocking you.
Can you do the same with Apple's app store? No you can't because tethering apps are not allowed on Apple's app store(whether you're on Wifi at home or carrier towers).