Canned vegetables aren't very nutritious, because they have to be cooked so long to preserve them. Furthermore, canning vegetables and meat is potentially dangerous because of botulism.

Source: have been canning last few weeks, info straight from the 'Weck' bible.

Look, I'm not picking sides here, but let's not look at the past with rose colored glasses. When I tell my aunts that I'm canning, they look at me like I'm nuts. They lived much of their lives having to can on a farm, and they love the ease with which they can live their lives now, and the options they have.