Because pickups were not generally available in europe so you wouldn’t bother unless you really actually genuinely needed one (e.g. forestry services), and many countries had automobile taxes which approximated power via displacement, so huge american-style engines led to absolutely prohibitive car tax rates (that’s why euro engines have historically been pretty small, and even completely weird e.g. the UK’s RAC horsepower didn’t even use displacement at all it only used bore, so a small-bore long-stroke piston was taxed significantly less than a large-bore short-stroke one, for the same displacement).