Musk stated (I think he just did some mental napkin math at one point) that if they meet their goals, the world's launch capacity will be expanded by two orders of magnitude. How often does any new development in any field bring about two orders of extra capacity? How does this incredible capacity change how you use this thing?
First consider prices. A launch would cost fuel + support operations + amortized cost of rocket. The last two will tend towards zero as they can be increasingly automated and will be a small fixed cost. IIRC, fuel costs roughly $60-100 per kilo to LEO, a 100kg person with 100kg of supplies and life-support equipment can reasonably expect to get to LEO for $20000 in fuel costs. Ok, so you need to "rent" the rocket (you want to stay there at least a few days), pay operations, SpaceX margin, R&D etc. Even then, imagine weekend LEO launches for $50,000 in the late 2020s. That's astounding. Given millenials' propensity for "experiences", they're going to have hoards of people buying this.
But what about risk? They've been trying to launch Crew Dragon for many years and still haven't. Well, with expandable rockets, you have to establish a safety record, it takes multiple flights, it's extremely expensive, you need a new rocket for each one. With fully reusable rockets, you can literally establish a safety record for an individual rocket within a matter of weeks, not years. Even launching once every three days (ie, far from their daily targets), it would take only a year to do more launches than Falcon or Arienne 5 have made in decades. Also, people are far more willing to take risks than organizations like NASA. Consider a thought experiment: SpaceX does 100 launches of Starship and establishes a safety record of 99% (1 blew up). They then start selling tickets, will people still buy, fully signing away any liability? Yes, you'll still have hoards of people lining up for a chance.
Finally, this is going to change science as well. Today, sending a 1 ton rover to the surface of Mars is a Really Big Deal. Hence, probes are made very carefully, very expensively and very very slowly. Not just design and build (it takes a decade), but operations as well (Curiosity traveled only 20km in the last 8 years). Everything is essentially super-low bandwidth. But once you know you can get a cheap ride to Mars (of anywhere else) any time, you don't have to go to such extremes. You can easily send more rovers, more radio relays, they can travel further, experiment more, take more risks and if you lose one, it's just not a big deal anymore!