Its also because of traffic regulations in Europe, the higher cost of petrol (until recently automatics were less efficient than manuals, especially with smaller engine cars) and "sunk costs".
Unlike USA if you take your driving test in an automatic car "code 78" is put on your licence - you can only drive automatic cars until you either take another driving test or (in France and Germany) a few hours of extra lessons (in those countries driving schools are more directly regulated by the Government).
Because of this, and younger people having less money for a first car, until recently it was more common to learn in a manual car and drive one for their first few cars (at least until knees start objecting to dealing with the clutch, and what is fun on a trackday becomes less so in busy traffic and with the abundance of roundabouts in many European countries!)
The situation is changing in last few years, especially with the rise in traffic levels - particularly in city areas, more younger people are learning in and driving automatics. Many may not be "car enthusiasts" as such and just want their licence quicker and to be able to get to places (although some are, and for them dual clutch (DSG) 'boxes are increasingly popular)
Older people who are already used to driving automatics (even if they learned in a manual) are also feeding the second hand market by upgrading to EV's and selling their old cars.
Incidentally Switzerland removed the distinction between licence categories recently (so it is same as USA), but one reason was for some years automatics had become more popular than manuals!