Space. It's everywhere and it's a conundrum. It's so empty and yet so full of promise and danger. It may be our future, and yet it will be the source of our ultimate demise. When we look up into the night sky we are full of both wonder at the endless inspiration and dread at the unfathomable immenseness.
It is in the role of inspiration that we may find our strongest need for a space program to fulfill. People, individually or as groups, desire to have meaning, to make a difference, to obtain a sense of purpose and ultimately a sense of achievement in some great endeavor. Many are inspired to study, learn and work in the sciences and having a program for their employment and competition is necessary for society to maintain a high level of proficiency. It also serves as a repository for the knowledge of certain technologies that might otherwise need to be maintained by a military-industrial complex.
A great endeavor such as laying the foundation of a space-access infrastructure is akin to the building of the pyramids in several ways. It's a highly visible project that will continue after the careers or lives of its participants. It's an achievement that would be remembered as a great wonder. And most importantly, it is a project that can pull people together from multiple countries all across the planet in unified effort for a program that will benefit all (possibly reducing the need for militaries as well).
There are also plenty of other reasons to go to space. We have less concern about tearing apart asteroids or lunar mountains for minerals, while on earth such widespread activities can devastate the environment and ruin people's lives. We might be able to find rare elements and minerals that might be useful in industry if they were to become available in suitable quantities. We might also be able to manufacture objects in ways that may be better than those manufactured on earth, a high pressure, high gravity environment. And, of course, there's always the potential save the earth from an asteroid impact.
A lot of people claim that space is too expensive and that we need to use our money and energy elsewhere in the economy because there's always someone who needs something else (starving kids somewhere, etc). Fortunately, the economy, including space endeavors, are not a zero-sum game. However, there are issues with cost over-runs and general inefficiency. Like most products and services, space access and infrastructure can benefit from economies of scale, if we were to go to space in a big way. Instead of having a single vehicle like the STS that served as an ascent vehicle, cargo lift, passenger craft, motel/Recreational Vehicle, lab, and re-entry vehicle, perhaps we could have different vehicles and structures for each. With more mobile launch paradigms we might be able to launch passengers to a space station with a short duration of free-fall, which would reduce the demands for long-term life support and associated mass, thus lowering expense. Over time, as we launch and build infrastructure all of these savings will produce a synergistic virtuous cycle for space access and for related industries and jobs on earth.
Private enterprise is a good start, although private business cycles tend to be too short for long-term investment, which requires something long-lived like government or religion or a dedicated social organization/society. If people are iffy on supporting it with taxes or fees, perhaps bonds could be issued with coupons redeemable in related novelties sourced from space or the ability to put something into space or be part of something put into space (off-world ash-burial?).
Personally, I've been space-happy since I was knee-high to a Skywalker. Star Wars was probably my first.... scratch that, Apollo 17 may have been my first memory, playing with a plastic Saturn V as a baby or toddler, as I was born shortly before the last mission. But Star Wars was formative and I begged to see it several times at the drive-in. And to explain how inspiring the movies were, I recall the drive home from the theatre in winter, I think, after watching "The Empire Strikes Back" and the snow in the headlights looked like stars zooming by like in hyperspace to my little wondering eyes.
But it's late and I'm rambling now. Does this help answer your questions?
Et tu BAUT? Quantum mutatus ab illo.