Talking about the Netherlands: when I got the theory part of my motorcycle license, I had to learn (and got tested on) all sorts of crazy traffic situations involving sidecars. Of course, I have never seen one in my entire 4+ decade life.
Oh God, we have those in Berlin, too. They're almost exclusively used by British beer tourists.
Freight bicycles are also in extensive use in Denmark.
Also very popular in Cambridge - which really just supports the point someone made in another thread that they're still common in regions that use motorcycles predominantly practically as opposed to sport/luxury/hobby. (Cambridge & NL have high bicycle density in general.)