you mean GURPS Traveller didn't? neither T20?... that will unshackle Traveller and make it generic.
like I said, traveller isn't the rules - 'cept, as pointed out earlier, things like jump and no ftl. not sure I'd call those rules though, more like setting.
traveller is huge, and difficult to run. beginning a game requires that both referee and players invest many days absorbing a very large quantity of information before the first dice are rolled, and as soon as the game begins the need for house rules becomes apparent. an official setting greatly simplifies both tasks, and rules based on the setting make the game more accessible and the inevitable house rules more coherent, and reinforce the setting. "generic" rules simply push off more work onto the referee, and leave him with no guidance except personal experience. the work load can become heavy.
do fans look for a ruleset, or a setting? I mean, I don't know, but I assume MongooseMatt does since he makes a living at it.