I've seen rounds where players would do the keycard mission, and it would end with Traitors stealing the datapad and flying away in Shuttle R87, leaving the Innocents behind to die on the Meridian, then being surprised when they see "Innocents Win." They've complained "Why should the Innocents win? We're the ones who escaped!"

Well there are multiple answers to that question. The first is balance. The second is lore. When you get onto the shuttle and fly away from the Meridian, you're completing the Innocents' mission, therefore making them win. Even if you've killed some of them, their objective was to escape with a datapad containing all of the files from the Meridian's computer systems, and by doing that for them, you're making them win. As soon as the R87 exits hyperspace at its destination, it will automatically transfer all the data to the command vessel.

Also, leaving the influence of the alien parasite that turned you into a traitor. So you're back to being an agent, living with the guilt of having betrayed and murdered your fellow agents.

As a traitor, your job is to make sure Innnocents can't leave the Meridian alive. If you decide to finish the round by stowing away on the Shuttle, THEN killing the Innocents after they take off and think they're home free, it's possible but you're still cutting it close. Once the shuttle is in motion, traitors can only win if all of the last innocents are onboard, and you kill all of them before the shuttle begins to fly forward to get in position to make its FTL jump. If you do it before that time, then Traitors can win, as it would be implied that the Traitors will have time to change the jump coordinates or delete/alter the files.

I've also heard some complaints about how when self destruct is triggered, Traitors can't get an easy win by stealing the shuttle and leaving the Innocents to die. This is also for balance. If traitors were able to start the shuttle after triggering self-destruct it would be too easy for them. Remember, as a traitor, it's still your job to make sure nobody leaves the Meridian alive. The lore reason? Well let's just say that after your tech specialist hacks the Meridian's systems and transfers all of their files to the shuttle's computer system, the shuttle also gets the DNA and fingerprints of the traitors, and those fingerprints are no longer on the approved list of people who can start up the shuttle