I think ultimately it's a business question. Virgin Galactic is selling tours at a premium price where as Concorde was sold to move people from point a to point b.
With Concorde, since the point of the craft was to get people from point A to point B very very quickly, they put money into big engines and efficient aerodynamics. The view doesn't really matter in that equation, but you do need structural integrity. So they went with the cheapest way to get that structural integrity, small windows.
Virgin Galactic, on the other hand, is selling an experience. And frankly, if you're going into space the two biggest selling points are going to be zero gravity and, honestly, the view. Hence, even though it will make the craft more expensive to reinforce properly, they are installing very large windows.
As a note, airliner manufacturers could also install big old huge windows if they wanted as well, but do you want to pay another $50 a flight just to have a bigger window? For most people the answer is no...hence small windows.
Basically it's just a matter of figuring out what you are trying to sell and, then, putting money into that selling point. It's what gets you a good return on your investment :).
PS- lol, and after all that writing I appear to have answered the "why" and not the "how". Well, let the internet judge me as it will, I'll leave this answer up for now :).