They're quite common in Belgium (from what I've seen), and I'm seeing them a lot in the Netherlands as well.

To my knowledge, in the case of the Netherlands, people are using a tax-loophole to import them into the country without paying the appropriate vehicle import tax. This is done by importing and registering the vehicle as a company vehicle, but using it as a personal vehicle as well

Importing an American pickup truck this way is still expensive, but not nearly as expensive as if they had to pay that tax.