I never considered He3 as the main reason.
The Moon has far more resources as a lure for colonization. Aluminum, titanium, oxygen, and other basic building materials are plentiful in the lunar regolith. Asteroid impact sites will have iron, nickle, and platinum group metals for extraction as well. The Moon's gravity can be used for industrial applications in areas where zero g would not be the best choice, but it's still low enough to allow for low cost launches.
