Not for those who are not sure about Linux. Installing an app and launching it, is a familiar task and quick to do, to take a look. No need get a usb stick and do unfamiliar steps right just then.
Then if Linux looks good, and you want to keep it, now you have the motivation to sort out how to install it. It's a different task.
Many people don't do that, because they dont know what Linux looks and feels like. So they won't install it.
WUBI did a good job of that.