Think about it: in 15 - 20 yrs time, with better improvement in Medical Science, more people will be able to live over 100 yrs old. How many of you think that your kid (1 child family?) will support you? If you are 100 yrs old, your kid will be 70 yrs old if you have 1 child at 30 yrs old. If they are the only kid in their family, they will need to look after you and their in-laws too.