"The first time I saw an American style SxS frig in a Brit broadcast was around 2002 in an episode of "Cash In the Attic" with Alister Appleton. "
Fitted kitchens in UK and Europe are just that, as such many for a variety of reasons chose small under counter fridges that fitted into cabinetry under counter.
Kitchens across the pond tend to be smaller, more compact and lacking light and counter space compared to what is found in USA. As such something would have to give if either say Hyacinth Bucket or Jean Mary Pargetter wanted even the (now more common) tall but narrow fridge/freezer.
As for rest of it in UK and across Europe for that matter kitchens tend to be far smaller than found in American homes. Not just flats but private homes as well. Latter is changing slowly over past few decades as new build private homes are growing larger, but still.
Other bits come down to cultural differences and household economy.
Energy costs in UK and Europe on balance are far more dear than most or all areas of USA. Fridges/freezers are some of the largest consumers of electricity in all households. As such it's not just price of fridge that comes into play but annual cost to run the thing.
Keep also in mind while gradually changing for UK and much of Europe when one leased a flat or bought a home often you had to fit out kitchen yourself; cabinets, appliances, the lot. Where money is no bother suppose buying huge fridge isn't an issue, but for others that may not be true.
Other cultural differences are fact many in UK and Europe still tend to cling to old ways. They purchase enough food for say a few days or week (including frozen) and thus don't see need for huge fridges or freezers. Americans are fond for some reason of laying in enough food to seemingly last duration, as if they'd just heard Hitler has invaded Poland or something.
Americans on average waste unconscionable amounts of food. They fill those large fridges or freezers with stuff that often sits and spoils or becomes damaged (freezer burn) thus must be thrown away. European way is far better, buy what you can consume readily and enjoy good fresh food.
https://energysavingtrust.org.uk/co...=The key reason for this,more energy to do so.
https://www.telegraph.co.uk/interiors/home/best-fridge-freezers/
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