That's where most of them hail from, I understand.
The "Air Tank on the Front" look wasn't that popular in these illustrations, but it does make sense. If you had to check the hose or valve, you'd want it right there.
The plot, as related by Bertram Chandler.com:
The reward for rescuing Thermopylae is finally paid, and Calver and his shipmates from Lorn Lady purchase a ship and rename her The Outsider. Two years are spent as a charter to Rim Runners, then six months tramping, before Sonya Verrill reappears and engineers a charter from the Federation Survey Service to look for an alien derelict. She accompanies Outsider, but proves very disruptive to Jane Calver.
Mostly chick-fights, then? Not many Outside Ships? Here's another description:
Beyond the laws of physics - into the unknown. Only one man ever survived contact with the Outsiders and Commander William Maudsley has always refused to speak of the horrors that destroyed his ship, murdered his crew, and left him a broken man. But there are always men willing to take great risks for the promise of great rewards: Derek Calver means to succeed where Maudsley failed. Despite the fears of the crew and vague rumors of terrible alien life beyond the rim, he will cross man's last frontier and enter the warped, unknown infinity "Outside."
Sounds like two different books. I suspect the second is promo copy and the first one was the truth.