How does it matter if I use data for my phone or my computer? To some extent I agree that this would end up costing higher when the carrier has unlimited data. But even there, if more people start "misusing" the connection (download songs, movies?) the price is going to go up and you don't need tethering to do that.

To give you a perspective: Tethering is available in India with every single connection. You just need a supporting phone (USB or WiFi). The plans are all capped there but so are most plans here. You guys seriously have to wake up and realise that you are severely restricted on everything from which phones you can buy to how you use your phone and what apps are installed. I mean, seriously!