>Either you save energy, drive less, etc. or you embrace energy sources like nuclear.

I took this to be an either or statement, apologies if that was not your intention.

>Anyways, I don't think I understand why I practically need both?

Overhauling the entire energy system is a huge effort, even more so when the demands grow year after year. Hitting that target in the requisite timeframe is much easier if the energy demands are lessened through conservation.