People work hard, earn livelihood and think that this is life. They are habitual to office life, commuting and enjoying yearly vacations.
While living like that they forget that they can't live like that forever. There would be a time when they will retire and all the expenses have to be borne by the corpus which they have created for the retirement.
But, this realization comes later in one's life. They think that retirement is not such an important topic.
They have an active life and retirement is far away. And this is the reason, people struggle in retirement, and they have to work even after retirement to fulfil their daily needs.
And the reason is they don't have enough money that can last longer. The money they have can last in a few years and after that, they are clueless about what would be like.
But, anyone can plan for retirement. The early you start, early you can retire if you wish because you can accumulate enough money.