I also invest 50-70%, but mostly because I have a very high-paying job and currently very low costs of living. Since I'm still young, I want to use my exceptional position to the max and invest as much as I can now, then let it sit and grow. If I'm lucky, this could enable me to retire early. If I'm unlucky, I could end up broke, the same outcome as if I squandered my high income on things I don't need (like many people would), and then continue on with a "normal" life.