I have put a lot of thought into this. I have several admittedly wierd ideas:
1. Controls now are a lot more precise. Your mouse or controller for your preferred console can sense any direction on a 2d plane, plus how far you push it to indicate speed or something. By comparison, a D-pad has eight directions and no pressure sensitivity, its just go or stop.
2. Marketing games that are really hard is incredibly difficult these days, what with casual gamers all over the place. This is why there are difficulty settings.
3. Since there is the possibility for more gameplay mechanics, the challenge comes from using a bunch in tandem rather than having super good timing or reflexes. This is apparently a lot easier.
4. HUD and better graphics make it easier to tell whats going on.
Thats all I can think of really. I may have more eventually but I dont feel like typing anymore.