I don't know about your parents, but my parents never had any snacks in the house (I grew up in the 70s). We ate at meals. While my father drank milk at meals (and ate butter out of the dish!), I hated the stuff and drank only water. We didn't have anything else in the house. Things like potato chips, etc, were things we ate at birthday parties.

We ate big meals, but we didn't eat anything else. When I see families now, they stock up with super mega sized snack food at Costco and cram it in their minivan (the 2 reasons for having a minivan being to drive soccer teams around and to take your super mega sized snack food home </snark>) When I was a kid, people didn't buy stuff at that scale. Homes were smaller too, as were refrigerators. You just couldn't do that kind of thing easily.

Of course, my excuse for getting fat these days is because I live in Japan and there is nowhere in Japan that isn't walking distance from a convenience store... That and my wife believes that beer has no calories -- a misunderstanding that I'm loathe to correct.