Darth Vader could have met with these guys in the hangar. It would have been easier and more secure–instead of giving these for-profit lowlifes a tour of the galaxy’s advanced Imperial warship, he could have met them in a more clandestine location and sent them back on their way. He could have even Space-Skyped the meeting, or just put out a Public Service Announcement.
He needed to send a message to his subordinates while keeping them alive. The message was “Hey, guys, you really stink at your job, so here’s the replacement crew. Look at them. They’re going to take your jobs because I trust them more than you, my own crew, the finest in the Empire. I’m replacing you with a lizard, a robot, a bug, a bug robot, a masked man, and a guy wrapped in toilet paper. Maybe they’ll be better at this than all of you, who have disappointed me so much. Look upon them. Look at them and understand my displeasure.”