It streamlines the whole release process, and brings the prices down. Having distribution for a small minority who don't want to get with this century would be harmful for the overall pricing and distribution. I do feel sorry for the small minority of people who can't get ready access to a broadband line, i.e. remote villages of Alaska or some places in foreign countries where there are fast, but heavily capped connections. For the vast majority of users, however, it works well.
Who says it is only a small minority? Perhaps on this forum, because we are all sort of tech interested. But out there it is not a small minority, at least here in europe. All the people I know who just use their computers for browsing, music and their pictures have just these usb internet sticks - often with a 3gb data limit here in austria.