It's the feeling of having to "hack" your iPhone to be able to do the things you want to do with it...
I have to do it, just because I want to be able to make a phone call with it over here in Holland. So, the most basic of functions forces me to hack it, and therefore I can also install 3rd party apps for fun.
But.... If the iPhone was made available in Holland, and once the iPhone 3rd party software becomes available via the AppStore, I know I don't want to hack my iPhone. I probably will buy a new "real" iPhone, and use it the way Apple intended me to. So, being able to update to the latest firmware without hassle, and knowing that all available 3rd party software will work perfectly.
ATM, you have to have faith in the Community....
Imagine having to "hack" your Mac (or PC) to let the latest version of Leopard work on it... Yeah you'll get it to work, but would you really be that comfortable with it? Knowing that every 10.5.x upgrade will probably break your OS (like the "generic Intel/AMD Leopard" install DVD's out there...)