社会構造の変化で、制度を支える現役世代の負担が大きくなりすぎたから。

The current pension system was designed during the high-growth economic period when the population was continuously increasing. However, in the present day with an advanced aging society and declining birthrate, the burden on the working generation that supports the pension system continues to grow. It is clear that maintaining the system as it is will become difficult. For this reason, discussions on painful reforms, such as raising the pension eligibility age and reviewing benefit amounts, have become unavoidable.