Don't forget the assumption that these are baby steps toward the eventual goal of colonizing space, a deeply dorky outcome
Hey! I resemble that remark....
But hey, I guess I'll own the dorky label. Because the thing is, I do believe that these are baby steps towards space colonization, and I think that colonization is just about the best possible good on the horizon that humanity could achieve. Earth constitutes a few tenths of a percent of the mass in the solar system excluding the sun. Only a fraction of that fraction is directly involved in our actual biosphere. It receives about 1 billionth of the sunlight the sun produces. And despite all that insignificance, it contains 100% of the known life in the universe.
So why would we want to continue to base our heavy industry, resource extraction, polluting population centers, and wars here indefinitely, when there is a billion times the living space and free solar energy available out in space (and that only counts our own solar system)? I consider it axiomatic that expanding the number of humans that can live quality lives is a good thing, and that allowing polluting industries to move outside our natural biosphere is also a good thing.
But let's just assume that you believe, for whatever reason, that humans will never do anything in space beyond our own planet's orbit. Well fine, there is still SO MUCH that we can accomplish in orbit, if we can only bring the price of launch down. How about Earth science missions, to track ocean currents and weather patterns and ice melt and methane release and land subsidence, in order to refine models of climate change? Lower launch costs for satellites, and you make those missions cheaper, more plentiful, and easier to iterate upon. How about expanding internet access to areas of the world that can't afford fiber (like for example my own home area)? How about solar power satellites, which have the potential to harvest many times the available power of ground based solar because they don't have to worry about clouds, atmospheric interference, or 8 hour nights, supercharging the transition from fossil fuels? What about mining the moon for raw materials for said projects, reducing both launch costs (as ironically it is energetically cheaper to move something from the moon's surface into low Earth orbit than it is to move it from Earth to low Earth orbit) and the environmental impact of things like silicon and iron extraction? And I'm not even going to get into the possibilities for pure science in orbit, as that typically isn't as convincing to someone airing the kinds of concerns that you mention.
I can't say for certain space development is coming. Obviously people made predictions exactly like this when we first landed on the moon, and here we are. But I do feel absolutely certain in saying that if an industrial space revolution is coming soon, it will be because of the pioneering efforts of companies like SpaceX, and to a lesser extent Blue Origin and even Virgin Galactic.
Thanks for the reply. Lots of good stuff here. This part above is specifically what appeals to me about this method. I see a huge market for smaller, cheaper, more frequent launches. We need work-horse methods of getting into space more than we need another extremely over-speced project like the shuttle.
Right now, the king of small cheap launches for cubesats and the like is rideshare on a Falcon 9 from SpaceX. It is by far the cheapest and most reliable option available, though you are essentially on someone else's schedule since you are hitching a ride on a bigger launch. But you just can't beat the price. Second place is probably the Electron rocket from Rocket Lab, which is a small launch vehicle from a company whose entire mandate is exactly what you are talking about, a workhorse small payload launcher which can be launched more often and easily than traditional large rockets. It's more expensive than SpaceX, but you get to have a whole launch dedicated to one or a couple small sats, so there are advantages.
There is a whole cornucopia of other launch companies aiming at that same smallsat market, and most have their own gimmick they are banking on; 3d printed rockets, rockets that can be deployed from shipping container sized mobile launch module, rockets that get caught by helicopter on descent for re-use, and so on. A whole explosion of evolutionary branches trying to get into the small launch market. But the thing that pretty much all of the credible players have in common is that they are still using the basic rocket-on-the-ground architecture to get up to space, nary a plane assisted launch in sight. Probably this is partly due to the massive and incredible success of the Falcon 9 and its reusability, but the engineering and economics of orbital launch just don't seem to look good for assisted launch these days.
This point, however, is where you lost me. Yes, this version doesn't reach orbit. But why the insistence that this style of launch never will? Isn't serious improvement in the technology the entire raison d'etre of Virgin Galactic? Is there anything fundamental to the design that means it will never be capable of these things? Does the smaller size make it physically impossible, or is it just something we haven't done yet? I don't grok the extrapolation.
Ok yeah, maybe I should have said "specific to Spaceship 2" rather than "Specific to Virgin Galactic". Spaceship 2, their current vehicle, is never going to reach orbit. It just doesn't have the power to reach orbit, and isn't designed to do so. According to the company, spaceship 3 is supposed to reach orbit when it eventually gets designed and built.
I do think that this tech will have some use cases. Like I mentioned, security payloads for spy satellites or antisatellite weapons is probably a big one. But if you are specifically talking about workhorse rockets, it looks like a rocket makes a better first stage for your rocket system than does an airplane.
Citation for entire above post: I'm a space nerd and not in any way an engineer or involved in the industry. So uh yeah, I could obviously turn out to be embarrassingly wrong.

But embarrassingly wrong with all the best intentions, and with massive hope for the future of humanity.