The classic Castle theme is the same as your childhood's favourite chocolate. You have fond memories, but when you try it again as an adult, you recognise that it is just industrial waste, and don't want it again. Translating this analogy to LEGO, the classic Castle/Pirates/Space themes are very outdated by today's standards, and people realise this quite quickly. Time has moved on, and what was considered great back then is lacklustre now. What people really want is going back in time and relive memories, but exactly the purchase of these sets makes them realise that it will not happen, it is a fool's hope, and just makes them feel old. To cope with growing up, people are looking for fresh things. No wonder LEGO is at its best when it feels fresh, that is what people really want.