Some programmes do work this way though, using U3 technology on memory sticks.
My opinion is that it *should* be how things work. The licence should be to the person, not the machine and if I want to use my Photoshop programme on a different machine then I should be able too.
Same with digital rights management. If I've bought a song, I should be able to listen to it on any player, any where, any time as long as it's my player.
This is of course the way Google is going with it's web applications, and it is certainly how big corporations run things. For example, when I worked at the BBC people had access to whatever programmes were needed for them to work. So everyone had Office, but only a few had Photoshop etc... I could have logged in on any of 30,000 machines and my programmes were there.