Demands not always lead market

There is a mystery. In some category of business, there is real demands but the market is getting smaller. This is a "business mystery". The business loan for small and medium sized enterprise and English conversation schools are the examples. What is the reason of this? It is difficult question. I think that this is because of the weakness of creating the new business. This means that in Japan there are a lot of chance to grow new business with "sleeping needs".