An interesting poll I wonder if the results reflect general attitudes or whether they are computer specific. For example, I have always been a documents hoarder and until recently always had a filing cabinet even in my home. As a result backing up computer data was second nature. My children (now in their thirties) don't keep any papers for more than a few minutes (a few weeks at the most) and don't backup computer data; probably a reaction to my hoarding. If they lose data they spend a few minutes cursing the manufacturer for supplying an unreliable machine and then forget about it.
If you can afford to waste your time recreating what you have aleady done, or if you regard what you have done as disposable then don't bother to backup. If you are going to backup then at least put the backup onto a different disk, preferably not in the same computer, and/or backup to removable media. If at all possible store the backup in another building or at least another room. {EDIT: sorry I see this advice has already been given but I guess repeating it cannot harm}