At any given time there's probably about 10,000 humans out in space. I'm not including the ones settling the inner solar system but more the ones who've ventured way way out. It's really hard to get out here because Earth doesn't have an established line of communication with any extraterrestrial civs.

It's not because Earth is some undeveloped backwater. Plenty of planets are decades behind us and still are connected to the greater interstellar community. It's because like I've mentioned before, interstellar travel is hard. With the damage to communication infrastructure the focus has been more on getting that back into shape instead of contacting new civs.

There are the illegal smuggling networks that crisscross the entire Arm. And those are usually how people get away from the planet. People looking for fun, adventure, or just a brand new start. They have no idea what's out there but they're ready to push off anyway. 

Some eventually make it back home, others are out here to stay. As of today Izzy might be considering herself to be in the latter category.