Because dictatorships are so famous for their 100 year horizons?
The USSR planned its world in 5-year spans. That's about the same length of time between elections in most democracies. Lots of people like to say things like "one of the biggest flaws of democracies" but I've yet to see such a statement that actually doesn't also apply to other systems of government.
Except china had the one child policy which clearly had long term goals in mind. Singapore also implemented eugenics policies and still has them to some degree.
Realistically population one of the few things you can take a long term view on, since so geo politics and technology are so unpredictable. With population planning much of the effects are only to come a generation later so mostly only a long term concern. It is also completely radioactive as far as modern democracies are concerned.
The USSR planned its world in 5-year spans. That's about the same length of time between elections in most democracies. Lots of people like to say things like "one of the biggest flaws of democracies" but I've yet to see such a statement that actually doesn't also apply to other systems of government.