I don’t have any definitive explainations for your, but the following are some certified Wild Ass Speculations.
Rinsing of dishes: Prior to the popularizations of dish detergents with high glycerin content ("…to avoid those dreaded dishpan hands"), plain soap or a very base detergent was used for washing dishes. Think of washing your dishes with Lava or that powdered crap you used to find in public bathrooms. Needless to say, it didn’t stick much and required little in the way of rinsing in comparison to Dawn or Palmolive. I remember washing dishes at my maternal grandparents–a pair of people who rejected wholesale any product that originated after 1950, to a point of actually purchasing and driving “vintage” cars long before they were hip–and the soap they used didn’t require any rinsing at all. On the other hand, it required a spectacular amount of elbow-grease to remove dried or burnt food.
Leaving stuff out: Same grandparents as above didn’t buy a “mechanical icebox” until it became essentially impossible to buy blocks of ice for an ice cabinet. As a result, they had very…conservative habits with regard to opening and using the refrigerator. Fresh fruits and vegetables were purchased in daily quantities if they didn’t come from the garden or last season’s canning, and so required no refrigeration. You’ll also find that many foods we commonly refrigerate do not require immediate refrigeration, especially if you plan to eat them soon. Hard cheeses, for instance, and eggs can survive for days at room temperature without ill effect. Uncured meat, of course, needs to be refrigerated to prevent bacterial growth, and most soft dairy products tend to spoil without cooling, but I’d wager that at least half the stuff in your fridge doesn’t require refrigeration.
Leaving stuff uncovered in fridge: In the days before Ziploc bags, Tupperware, and Saran Wrap, you just wrapped your meat in wax paper and tossed cheese onto a plate and let it go.
From what I’ve seen, most Europeans raised in the pre-1980 period tend to have enjoyed a standard of living that had fewer of the modern conveniences than that in the United States; that is to say, amenities were less available or more costly than on the west of the pond. Of an Welsh-English couple I knew a few years ago, for instance, one didn’t have a television in their house at all until the early Seventies, and the other was sans refrigeration for the first few years of his life (early-mid Sixties) and then when they did have one it was just roomy enough for eggs, milk, a small ham, and a few pints of beer. It wasn’t a big hindrince, as breakfast and lunch was some form of Bovril on bread, and stay-at-home mom usually made dinner fresh.
I’d guess that your in-laws are probably from that generation where habits based on those limitations were formed, and owing to the retardation of consumerism in Europe as a result of reconstruction following WWII that mentality probably exsisted somewhat longer than in the US.
Tomatoes in the fridge, though…I have to agree; that’s just wrong.
Stranger