My guess is that it's because Europe consists of relatively rich societies (so home computers were available since the 80s) that had limited access to US softwa

My guess is that it's because Europe consists of relatively rich societies (so home computers were available since the 80s) that had limited access to US software (pre-Internet, software availability over here was pretty hit and miss). That led to an active European freeware, shareware, and eventually open source software scene.