[CROSSHIGHWAYMAN]

I envision three ways for humans to leave this planet in the distant future.

1. Necessity.....we will use up all the raw materials and energy supplies and or be threatened with extinction from an asteroid impact.

2. World wealth will grow to where anything is affordable.

3. Earth will be visited by friendly aliens.

[MagnumRancid]

I think there are more possibilities than three, and I actually don't believe in "Friendly Aliens".
Profit could be a great motivator. There is money to be made in space, big money. The development, tooling, and infrastructure building requires the government,most likely.
I would not be surprised if the first "space colonists" were some religious sect or cult.
The author of the article is correct that robots could do the exploration and most of the work more efficiently and economically than humans. We're going out there. Out of necessity or curiosity, we're going. I won't live long enough to see it but my granddaughter might.